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Cell Bio 4
Terms in this set (398)
Draw the cell cycle
Red blood cells are constantly turning over
and have to be replaced by hematopoietic stem cells
Cells evolved from
unicellular to clonal than multicellulcar
Synthesis of RNA and proteins occurs continuously during cell cycle, DNA synthesis only
occurs during S-phase
During early embryonic development
cells divide synchronously until a certain point
Cell division rates
depend on the amount of nutrients present
Sea urchin was instrumental in the discovery of
proteins regulating the cell-cycle
How were essential components of the cell cycle discovered
Yeast models were used for genetic analysis of cell cycle control and the Sea urchin was used for biochemical analysis of cell cycle
The most common type of mutation, a base-pair substitution in which the new codon makes sense in that it still codes for an amino acid.
Conditional mutations allow the protein to function properly
in one condition but not in another (temperature is the condition for these experiments)These mutations are most often missense mutations that destabilize or disrupt protein interactions at the restrictive temperature (high temperature)
cell division cycle
Epistasis experiments can determine
the order in which these genes function during the cell cycle
A type of gene interaction in which one gene alters the phenotypic effects of another gene that is independently inherited.
Maturating Promoting Factor
MPF turns out to consist
of a cyclin and a cdk
Cdk activity depend on binding of cyclins
Besides cyclins, many other proteins regulate Cdk activity
many regulatory proteins regulated by protein degradation
Draw the 2-step CDK activation
A second phosphorylation event can inactivate Cdk (draw)
Cdk can also be inhibited by binding of Cdk inhibitor proteins (CKIs)
Two main families of Cdk inhibitors (CKIs)
SCF (skp1, cullin, F-box) controls proteolysis of Cdk/cyclin modifying proteins
Different F-box proteins in SCF provide substrate specificity
The anaphase promoting complex (cyclosome) is the key factor regulating proteolysis of cyclins
binds to cdk before mitosis, triggering mitosis machinery
Control of early vs. late embryonic cell cycles
Protein degradation via APC is required for the completion of mitosis
CDC20-APC/C promotes the metaphase to anaphase transition
is a protein involved in control of the metaphase-anaphase transition and anaphase onset. Following bi-orientation of chromosome pairs and inactivation of the spindle checkpoint system, the underlying regulatory system, which includes ___, produces an abrupt stimulus that induces highly synchronous chromosome separation
Draw how CDKs progress cells through the cell cycle (ie retinoblastoma)
A single CDK (M-CDK) is responsible for bringing about the diverse rearrangements at the beginning of mitosis
1.Assembly of the mitotic spindle
2. Ensure chromosomes are atached to spindle
3. Chromosome condensation
4. Nuclear envelope breakdown
5. Actin cytoskeleton rearrangement 6. Reorganization of golgi and ER
Type of signaling that secretes a molecule that makes a cell express genes that it wouldn't otherwise do
Visualizing the cell cycle in living cells
Somehow a cell can tell how big it is
and will divide when it is the right size
G1 phase, or Growth 1/Gap 1 phase
is the first of four phases of the cell cycle that takes place in eukaryotic cell division. In this part of interphase, the cell grows in size and synthesizes mRNA and proteins in preparation for subsequent steps leading to mitosis. G1 phase ends when the cell moves into the S phase of interphase
The phases of the cell cycle
G1, S, G2 Mitosis and cytokinesis
is a growth mechanism which functions to keep cells growing into a layer one cell thick (a monolayer). If a cell has plenty of free space, it replicates rapidly and moves freely. This process keeps happening until the cells have divided so many times there is no longer any room in the layer for them to replicate. At this point, normal cells will stop replicating.
The encoded protein binds to and prevents the activation of cyclin E-CDK2 or cyclin D-CDK4 complexes, and thus controls the cell cycle progression at G1. It is often referred to as a cell cycle inhibitor protein because its major function is to stop or slow down the cell division cycle.
Transforming growth factor beta (TGF-β)
causes synthesis of p15 and p21 proteins, which block the cyclin:CDK complex responsible for Retinoblastoma protein (Rb) phosphorylation. Thus ___ blocks advance through the G1 phase of the cycle. In doing so, ____ suppresses expression of c-myc, a gene which is involved in G1 cell cycle progression.
Myc protein is a transcription factor that activates expression of many genes through binding on consensus sequences (Enhancer Box sequences (E-boxes)) and recruiting histone acetyltransferases (HATs). It can also act as a transcriptional repressor. By binding Miz-1 transcription factor and displacing the p300 co-activator, it inhibits expression of Miz-1 target genes. In addition, myc has a direct role in the control of DNA replication
is a protein or complex of proteins that allows an origin of replication to begin DNA replication at that site. They are thought to primarily occur in eukaryotic cells, since prokaryotes use simpler systems to initiate replication
Anaphase-Promoting Complex (also called the cyclosome or APC/C)
is an E3 ubiquitin ligase that marks target cell cycle proteins for degradation by the 26S proteasome. The APC/C is a large complex of 11-13 subunit proteins, including a cullin (Apc2) and RING (Apc11) subunit much like SCF. Other parts of the APC/C still have unknown functions, but are highly conserved.[
Embryonic cells within the first couple of cell divisions after fertilization are the only cells that are
Stem cell niche
refers to a microenvironment where stem cells are found, which interacts with stem cells to regulate cell fate. This word can be in reference to the in vivo or in vitro stem cell microenvironment
Hematopoietic stem cells (HSCs)
are the blood cells that give rise to all the other blood cells and are derived from mesoderm. They are located in the red bone marrow, which is contained in the core of most bones.
a shortened chromosome produced when a large portion of chromosome 22 is exchanged with a small fragment from a tip of chromosome 9
originally described as a gap between mitosis and DNA replication; now appreciated to be the
time when cells grow and check for DNA damage and sample the environment to make the
pivotal decision to replicate their genomes and progress through the cell cycle.
when the genome is replicated
originally described as a gap between DNA replication and mitosis; now appreciated to be the
time when cells check for completion of DNA replication before entering mitosis.
Mitosis and cytokinesis separate the replicated genome into two daughter cells.
Most differentiated cells in higher eukaryotes withdraw from the cell cycle into this stage.
G1 restriction point
Monitors cell size, environmental conditions, and interactions with neighbors and
G1/S DNA damage checkpoint
Stops the cell cycle if DNA damage is detected
G2/M DNA damage checkpoint
A protein kinase cascade stops the cell cycle until all DNA is replicated.
Metaphase spindle assembly checkpoint:
Delays separation of daughter chromatids until all are
attached to the mitotic spindle.
Biochemical experiments on protein synthesis in early
embryos revealed proteins
named cyclins that are
synthesized and destroyed in synchrony with cell cycle
Humans have >10 Cdk
and 16 cyclin genes.
Phosphorylation of an activation loop (called the "T-loop")
threonine stimulates activity and
phosphorylation of another threonine promotes binding to cyclins
Cyclin binding activates Cdks by altering the conformation of the active site; thus Cdk activity
fluctuates across the cell cycle with the cellular cyclin levels.
Particular cyclins are synthesized
and degraded for each cell cycle transition
Phosphorylation of a tyrosine and a threonine inhibits activity
removal by the Cdc25 tyrosine
phosphatase promotes activity
Two classes of protein inhibitors bind Cdks:
CKIs (cyclin-dependent kinase inhibitors) and INKs help
to control Cdk activity in the G1 and G0 phases of the cell cycle.
Cells exit from mitosis when APC/C degrades
the cyclins required for mitotic Cdk activity.
a G1/S E3 ubiquitin ligase dependent on phosphorylation.
In G1 phase Cells exit from mitosis when
APC/C degrades the cyclins required for mitotic Cdk activity and cells either grow or enter a noncycling G0 phase
During the G1 restriction point the Prerequisites for replicating the genome and continuing through the cell cycle are
Adequate cell size No DNA damage. There must be nutrients and growth factors.
Transcription activator - when heterodimer with DP1 ---inhibitor when bound to Rb
Tumor suppressor pRb
Loss of function mutations predisposes to eye tumors called retinoblastomas
In the absence of growth stimuli, the complex of E2F/DP1, pRb, and histone deacetylase
targets and represses genes required for cell cycle
progression by chromatin compaction in the G1 checkpoint
Cdk4/cyclin D phosphorylates pRb,
dissociating the repressive complex, which allows for acetylation of local chromatin and expression of genes required for cell cycle progression in the G1 phase
Active p53 can arrest the cell cycle in G1
by stimulating the expression of Cdk inhibitors or can induce cell death
Adhesion to neighboring cells via cadherins mediates
"contract inhibition of growth"
Cells in G0 can re-enter the cell cycle
when stimulated by growth factors
An assembly of proteins called origin recognition complex (ORC) binds (yeast) origins throughout the
and helps to organize a larger assembly called the prereplication complex that is required to
"fire" the origin to begin DNA synthesis
ORC or origin recognition complex
is a multi-subunit DNA binding complex (6 subunits) that binds in all eukaryotes in an ATP-dependent manner to origins of replication.
Site on a chromosome at which DNA replication begins. where initiator proteins aggregate
prereplication complexes assemble
during the G1 phase
Cyclin-dependent kinases inhibit assembly of prereplication complexes
and therefore they assemble
only once after mitosis when Cdk activity is low prior to passing the restriction point.
A protein (called geminin) inhibits assembly of prereplication complexes
APC/C destroys geminin
during mitosis, allowing prereplication complexes to assemble in G1
Some of the factors required to assemble the prereplication complex may only interact with
chromosomes during mitosis,
since they are excluded from interphase nuclei by the nuclear pores.
Thus, these "licensing factors" can act only once per cell cycle.
A combination of mitotic kinases triggers the onset of DNA replication. This involves the following
Synthesis of Cdks, proteins that fire the origins and replication proteins (such as DNA polymerase) as
the cell passes the restriction point.
Activation of Cdks by phosphorylation and dephosphorylation.
Inactivation of Cdk inhibitor p27 by SCF
Histone genes are activated during S phase to double the histone content of the cell by means of the
Increasing transcription of the numerous histone genes.
Increasing the rate of histone mRNA processing.
Stabilizing histone mRNAs from degradation.
Newly replicated DNA is packaged
in new nucleosomes
Centrosomes duplicate by a semiconservative mechanism closely linked to the cell cycle
Cdks (Cdk2/cyclin E or cyclin A) regulate
the centrosome replication, but the phosphorylated targets are not known.
Mother and daughter centrioles remain linked (when)
from mitosis through G1
, S, and G2
During S phase new daughter centrioles form orthogonal to the existing centrioles,
which are then called
the old mother centriole and new mother centriole.
New daughter centrioles elongate until they reach full size early in mitosis
when the two mature
centrosomes separate to form the poles of the mitotic spindle.
In preparation for mitosis, cells synthesize cyclin B,
which associates with Cdk1 (the animal homologue
of the famous fission yeast kinase Cdc2) present throughout the cell cycle but not active until the
transition into M phase
Battling kinase and phosphatase activities regulate Cdk1/cyclin B
CAK kinase (Ckd7/cyclin H) phosphorylates
Cdk1, opening the active site for substrate
binding, but this does not turn on
Cdk1/cyclin B, since
Wee1 (and a related kinase myt1) phosphorylate
inhibitory sites that hold the Cdk1/cyclin B
kinase in check,
Polo kinase (PlX1 in the illustration) activates
Cdc25 phosphatase removes inhibitory
phosphates from Cdk1,
Cdk1/cyclin B also activates Cdc25 phosphatase,
creating a positive feedback loop for
Cdk1/cyclin B activation,
inhibits Cdk1 by phosphorylating it on two different sites, Tyr15 and Thr14. Cdk1 is crucial for the cyclin-dependent passage of the various cell cycle checkpoints. At least three checkpoints exist for which the inhibition of Cdk1 by Wee1 is important:
Ataxia telangiectasia mutated (ATM) is a serine/threonine protein kinase
that is recruited and activated by DNA double-strand breaks. It phosphorylates several key proteins that initiate activation of the DNA damage checkpoint, leading to cell cycle arrest, DNA repair or apoptosis. Several of these targets, including p53, CHK2 and H2AX are tumor suppressors.
The G2 checkpoint monitors for DNA damage or
incomplete replication and delays the
cell cycle in late G2 to provide time
for DNA repair mechanisms to
correct the problems.
Failure of this checkpoint allows cells
with damaged DNA to attempt
division, often leading to cell death.
The G2 DNA damage checkpoint shares
components with the G1 DNA
damage checkpoint and Two types of protein complexes sense DNA damage (by an unknown mechanism).
ATM kinase phosphorylates Chk1 (checkpoint kinase 1),
which activates Chk1 to phosphorylate an
inhibitory site on Cdc25, preventing activation of Cdk1/cyclin B and entry into mitosis
ATM kinase phosphorylates p53
which activates p53 to promote expression of Cdk inhibitors,
leading to arrest of the cell cycle
Cyclin B is a mitotic cyclin
The amount of cyclin B (which binds to Cdk1) and the activity of the cyclin B-Cdk complex rise through the cell cycle until mitosis, where they fall abruptly due to degradation of cyclin B (Cdk1 is constitutively present). The complex of Cdk and cyclin B is called maturation promoting factor or mitosis promoting factor
activates the cyclin-CDK complex by phosphorylating threonine residue 160 in the CDK activation loop. ___ itself is a member of the Cdk family and functions as a positive regulator of Cdk1, Cdk2, Cdk4, and Cdk6.
The "incomplete replication checkpoint"
also involves ATM kinase, which activates Wee1,
strengthening the inhibition of Cdk1/cyclin B and delaying entry into mitosis.
Defects in the genes for ATM or p53
predispose to cancer, most likely from defects in the G1 checkpoint
rather than from the G2 checkpoint
Cells have biochemical mechanisms to repair damaged DNA, including
replacement of damaged or mismatched bases and even double-strand breaks.
If genome replication is complete and the G2 checkpoint finds no DNA damage, then
a cascade of
reactions triggers the transition from G2 into mitosis:
Polo kinase activates Cdc25 phosphatase, which removes inhibitory phosphates from Cdk1.
Active Cdk1/cyclin B also activates Cdc25 phosphatase, creating a positive feedback loop for
Cdk1/cyclin B activation.
Accumulation of active Cdk1/cyclin B in the nucleus pushes the cell into mitosis.
Chromosomes condense in the nucleus, nucleolus disassembles, and duplicated centrosomes
separate to opposite sides of the nucleus and organize the two poles of the mitotic spindle.
Nuclear envelope disassembles and microtubules growing from the poles seek and attach
to kinetochores of condensed chromosomes
Interactions with microtubules align chromosomes in a plane between the poles; the "metaphase checkpoint" delays mitosis until all chromosomes are attached to the spindle.
Severing of physical connections between sister chromatids allows them to separate and
move toward the poles of the mitotic spindle (anaphase A). The poles of the spindle also move apart
The chromatids complete their movements to the poles, and the nuclear envelope reforms
around clusters of separated chromatids
Beginning in metaphase and continuing through anaphase, a contractile ring of actin
filaments, accessory proteins, and myosin-II assembles around the equator of the cell midway
between the poles of the mitotic spindle. In telophase the contractile ring begins to constrict the
equator around the remnants of the central spindle (mid-body). Fusion of the plasma membrane
completes cell division
Draw the mitotic phases of the cell cycle
Prophase in detail with regards to chromosomal condensation
Changes in the nucleus that lead to chromosome condensation:
Cdk1/cyclin B phosphorylates condensin, which promotes its accumulation in the nucleus.
Cdk1/cyclin B and aurora B kinase also phosphorylate histones.
Together active condensin and histone modifications promote condensation of each chromosome into
a thread visible on light microscopy.
Sister chromatids are paired from end-to-end by cohesin.
The nucleolus disperses.
Prophase in details with regard to the cytoplasm
Maturation of centrosomes: Polo kinase and aurora A kinase promote association of γ-tubulin ring
complexes with the centrosome, resulting in more active nucleation of microtubules in mitosis
than in interphase.
Microtubules are more dynamic and shorter than in interphase owing largely to a reduction in the
probability of rescue; this dynamic state allows them to search for kinetochores.
Cdk1/cyclin B (and possibly other kinases) phosphorylate nuclear lamins, causing them to
disassemble along with most other intermediate filaments.
The Golgi apparatus disperses into vesicles: Budding continues while Cdk1/cyclin B phosphorylates
and inhibits a protein required for fusion of transport vesicles back to the Golgi apparatus.
Endoplasmic reticulum breaks up into vesicles.
Cdk1/cyclin B phosphorylates elongation factor EF2a, which stops protein synthesis.
Nuclear Changes in Prometaphase
Following disassembly of nuclear lamins, the nuclear envelope with associated lamin B breaks up
into vesicles or is included with fragments of endoplasmic reticulum.
Lamin A and nuclear pore components disperse in the cytoplasm.
Kinetochores form discrete structures capable of binding microtubule plus ends.
Mititotic Spindle structure during prometaphase
Bilaterally symmetrical: Radial arrays of microtubules emanate from both poles and interact with the
chromosomes between the poles.
Microtubules minus ends associate with the poles, and plus ends probe the surrounding area.
Astral microtubules: Plus ends radiate out from each pole.
Kinetochore microtubules: Kinetochores capture plus ends and reduce the chance of catastrophes;
kinetochores of paired sister chromatids attach to microtubules from opposite spindle poles.
Growth and shrinkage of kinetochore microtubules and the action of motors move the chromosomes
to the mid-plane of the spindle.
Interpolar microtubules: Plus ends overlap with microtubules from the opposite pole and are coupled
to them by both plus end-directed kinesins and minus end-directed kinesins.
Spindle structure is determined by the dynamics of the microtubules and the actions of at least seven
kinesins and a dynein, which produce forces on microtubules and kinetochores.
Chromosomes oscillate back and forth on
the metaphase plate between the poles
In metaphase Kinetochore microtubules
maintain a constant length but treadmill slowly by
addition of tubulin dimers at the
kinetochores balanced by loss at the
Kinetochores lacking attached microtubules bind
protein kinases (BubR1) that inhibit the
transition to anaphase through a series of
interactions: BubR1 phosphorylates
Mad1p II, Mad1p activates Mad2p II,
and Mad2p inhibits APC/C.
Changes in the mitotic spindle during anaphase
Anaphase A: Kinetochore microtubules shorten, and motors associated with kinetochores pull the
kinetochores toward the poles.
Anaphase B: Bipolar kinesins interact with the overlapping, antiparallel interpolar microtubules to
push the poles apart. Interpolar microtubules also elongate in some cells.
Activation of APC/C leads to ubiquitin-dependent proteolysis of the following during anaphase
Cyclin B (required for exit from mitosis) and
Securin (required for separation of sister chromatids); securin inhibits the protease separase which
degrades cohesin, an SMC protein that holds sister chromatids together. Therefore, destruction of
securin allows separase to digest cohesin and release sister chromatids.
Draw and explain the separation of chromatids during the metaphase anaphase transition
Draw spindle elongation
kinase involved in spindle checkpoint function. The protein has been localized to the kinetochore and plays a role in the inhibition of the anaphase-promoting complex/cyclosome (APC/C), delaying the onset of anaphase and ensuring proper chromosome segregation.
Telophase in detail
Once the chromosomes reach the poles, the nuclear envelope reassembles on their surfaces. Lamins are dephosphorylated; they bind chromatin and anchor nuclear envelope vesicles to the
chromosomes. These vesicles fuse to form a continuous nuclear envelope. Nuclear pores reassemble and transport lamin A back into the nucleus for incorporation into lamin
Separation of daughter cells at the end of mitosis depends on the formation and
constriction of an equatorial "______" composed of actin filaments, myosin-II, and associated
Inventory of proteins required for cytokinesis
Cytokinesis of Drosophila and fission yeast depends on
the same set of ~30 proteins, but the regulatory networks are not well understood
Constriction of the contractile ring
Well after the contractile ring assembles around the equator, a still mysterious signal triggers its
constriction. In some cells this involves transient release of Ca2+ around the equator and likely
activation of myosin light-chain kinase, which turns on the contraction. The contractile ring disassembles as it constricts around the remnants of the central spindle. The central spindle condenses into a tightly packed overlapping array of microtubules called a mid-body, which occupies the intercellular bridge between the daughter cells
Membrane fusion machinery
is required to complete the division of the cells.
SMC proteins (Structural Maintenance of Chromosomes)
represent a large family of ATPases that participate in many aspects of higher-order chromosome organization and dynamics.
is crucial for the localization of Mad2 to kinetochores, where Mad2 interacts with Cdc20
is a key component of the spindle checkpoint, a device that controls the fidelity of chromosome segregation in mitosis
Correlation of lung cancer and smoking
Evolution of multicellularity and modulation of the cell cycle
Explain how cancer cells become more heterogeneous as they progress
with more mutations cancer cells can be different from each other
Cancer cells compete with eachother in a darwinian style mechanism
During metastasis cancer cells must survive and proliferate in a foreign environment
Cancer is not communicable but there are rare examples in other animals
Immune cells that circulate within the hemolymph of insects and ingest foreign substances by phagocytosis; secrete antimicrobial peptides
Cancer for clam blood cells are contagious
cancer that begins in the skin or in tissues that line or cover internal organs. There are a number of subtypes of carcinoma, inclyuding adenocarcinoma, basal cell carcinoma, sqamous cell carcinoma and transitional cell carcinoma
Properties of transformed [cancer] cells
1. Lack of density dependent inhibition of cell growth
2. Reduced requirement for Growth Factors
3. Loss of contact inhibition
4. Alterations in the ECM and Cytoskeleton
5. Protease secretion especially metalloproteinases.
6. Secretion of growth factors promoting angiogenesis
7. Failure of normal differentiation
8. Failure to undergo Programmed cell death. [Apoptosis]
9. Transformed cell can cause tumors when injected into susceptible
10. Transformed cells have glycoproteins and glycolipids in their
plasma membranes making their membranes more fluid than
11. Aneuploidy: Aberrant chromosome number.
13. Failure of immunological surveillance.
14. Altered metabolism (Warburg Effect).
cancer that begins in bone, cartilage, fat, muscle, blood vessels or other connective or supportive tissue.
cancer that starts in blood forming tissue such as the bone marrow and causes large numbers of abnormal blood cells to be produced and enter the blood
lymphoma and myeloma
cancers that begin in the cells of the immune system
Central nervous system cancers
cancers that begin in the tissues of the brain and spinal cord
The great hallmark of cancer is that they lose
A gathering together in a state of contact inhibition
The hippo pathway
mediates contact inhibition
A model for an E-cadherin-mediated Hippo signaling pathway
Hippo pathway mediates contact inhibition of the cell cycle
Cells that lack contact inhibitions
also compromises the structure of the tissue
A type of gene that makes a protein called a tumor suppressor protein that helps control cell growth. Mutations (changes in DNA) in tumor suppressor genes may lead to cancer. Also called antioncogene
A normal gene that, when mutated, can become and oncogene
A gene that is a mutated (changed) form of a gene involved in normal cell growth. Oncogenes may cause
the growth of cancer cells. Mutations in genes that become oncogenes can be inherited or caused by being exposed to substances in the environment that cause cancer.
How oncogenes react during mutation
How tumor suppressors react during mutation
Some examples of how a proto-oncogene becomes an oncogene
Heritable epigenetics change
can silence a tumor suppressor
Oncogenes can promote tumor formation by causing increased cell division or decreased apoptosis
Oncogenes can be classified
into at least 6 classes
2.Growth factor receptors
3.Protein kinases or their activators
including all Ras family members,
4.Cell cycle control proteins
5.Proteins regulating programmed
cell death. [Apoptosis]
You can detect oncogenes
Genes and the related type of cancer (state each genes function)
Cells with one functional copy of a tumor suppressor gene
will usually proliferate faster than
The Ames test for chemical mutagens
Explain how the ames test functions
it is explained
Cancer cells have an altered metabolic state (called Warburg effect)
How to find tumors via Pet Scan
you administer to the patient radioactive glucose to see where the glucose will aggregate in the body
A cell needs multiple mutations
to become cancer
Draw and explain how cells can pass the restriction point inappropriately
E2f is a
The central role of p53 (draw)
cancer stem cell
Mechanism of HPV bypassing restriction point
a protein that can act as an anchor for cadherins or as a transcription factor (induced by the Wnt pathway); important in the specification of germ layers.
The canonical wnt signaling pathway
Cancer metastasis requires an epithelial to meschymal transition
EMTs involve loss of cadherin mediated adhesion
Another example of regulation of retinoblastoma (draw)
Having onle one funtional copy of the Rb gene predisposes one to cancer
Explain the difference between Hereditary and non Hereditary retinoblastoma
Why does loss of Rb predispose people specificall to Retinoblastoma
Brca-1 in DNA damage signaling
Parp Inhibitors Kill Cancer cells that Have Defects in Brca1 or Brca2 Genes
The Philadelphia chromosoome cause s an activating of Abl to be produced
Small Molecules can be designed to inhibit specific Oncogenic proteins
Small Molecules can be design to inhibit specific Oncogenic proteins 2
Many Cancers may be treatable by enhancing the Immune Response against the specific
Cancer cells can tell T cells not to attack them. So we make drugs to stop that.
Combination therapies may succeed
where treatments with one drug at a time fail
Viral genome intergration
leads to cancer
List some of the cellular changes associated with EMT
In animal development, a series of cell and tissue movements in which the blastula-stage embryo folds inward, producing a three-layered embryo, the gastrula.
How is EMT similar to gastrulation?
Increased tumor invasiveness and metastasis evoked by VEGF Inhibitors
epithelial to mesenchymal transition
The phildelphia Chromosome causes an active form
of Abl to be produced
Modulatuion of inter-digit cell death has been
utilized during evolutionary adaption. Tgf beta signalling pathway is involed in apoptosis. The gremlin pathway can inhibit the bmp pathway. Fgf further eliminates cell death
The role of survival factors and cell death in adjusting the nuber of developing nerve cells to the amount of target tissue
More nerve cells are produced nthan can be supported by the limited amount of survival factors released by the target cells. Therefore, some cells receive an insufficient amount of survival factors to avoid apoptosis. This strategy of overproduction followed by culling ensured that all target cells are contacted by nerve cells and that the extra nerve cells are automatically eliminated
further inhibits BMP
Some Functions of PCD in Animal Development
(A and B) Sculpting. (C
and D) Deleting unwanted structures. (E) Controlling cell numbers. (F
and G) Eliminating nonfunctional, harmful, abnormal, or misplaced
programmed cell death which includes apoptosis and necrosis
Apoptosis differs from necrosis in that necrosis
During necrosis, cells swell causing the plasma membrane to burst and release the contents of the cell
is used in inter digit formation
Apoptosis has stereotypical features
Necrosis has stereotypical features
Via apoptosis in early development
you can tell the exact amount of cells that die
Genetic dissection of programmed cell death in nematodes
Interactions among egl-1, ced-9 ced-4 and ced-3 using genetic epistasis experiments
ced gene stands for cell death abnormal. egl means egg laying defective
If you over express ced-4 and ced-3
can kill a lot of cells
Evolutionary expansion of C. elegans apoptotic machinery in mammalian cells.
Apoptosis is promoted by the release
of cytochrome c into the cytosol from mitochondria.
There are two types of apoptosis
one being intrinsic and the other extrinsic
Apoptosis Depends on an Intracellular Proteolytic Cascade
That Is Mediated By Caspases
Procaspase activation during apoptosis.
Family of cystein proteases that are activated at early stages of apoptosis and are responsible for degradation during cell death. They also cleave themselves to function
also known as zymogens where the prodomain gets cut off so a caspase can form
A few of the proteins cleaved by caspases
Explain how initiator caspases signal to executionary caspases
Nucleases that digest DNA during apoptosis
Caspases drive nuclear disassembly
in apoptosis. Nuclear lamins as well a Parp
PARP is involved
in DNA breaks
Inactive CAD is bound to
Caspases break down
ICAD to set CAD free
Draw the pathway of apoptosis
allows the visualization of apoptotic. Where you label the ends of DNA
High-energy electrons are transferred between
three repiratory enzyme complexes
Cytochrome C has two lives
it is used in aerobic respiration and in apoptosis
The three classes of Bcl2 proteins
Bcl2 Proteins Regulate
the intrinsic pathway of apoptosis and These proteins lead to the realease of cytochrome c
How Bcl-‐2 proteins work
Puma tells cell to die
BH3 proteins monitor
THe role of BH123 pro-apoptotic Bcl2 proteins (mainly bax and bak) in the release of mitochondrial intermembrane proteins in the intrinsic pathway of apoptosis
BH3 proteins differ in killing potential
Some killers have better attachment affinity
How pro-apoptoticBH3-only and anti-apoptotic Bcl2 proteins regulate the intrinsic pathway of apoptosis.
How pro-apoptoticBH3-only and anti-apoptotic Bcl2 proteins regulate the intrinsic pathway of apoptosis. Part 2
Recall that p53 activates genes involved in apoptosis
The extrinsic pathway of apoptosis
activated through Fas death receptors. Fas
A proposed model for the roles of IAPs and anti‐IAPs in the control of apoptosis in mammalian cells.
IAP's will block caspases if the procaspace cleaves
IAP stands for
Inhibitors of apoptosis
Phagocytosis of apoptotic cells
A proposed model for the roles of IAPs and anti‐IAPs in the control of apoptosis in mammalian cells. part 2
When cytochome c is release anti-iap is also released
Three ways that extracellular survival factors can inhibit apoptosis.
Fadd adapaptor aggregates
to form the Disc complex which is similar to the apoptosome
contains the fas ligand which attaches to the death receptor
Aging related diseases
Relative benefit of curing specific diseases vs. slowing the aging process
Life span increases
Evidence for the genetic control of aging
daf2 codes for an insulin like growth factor. Both genes are involved in metabolism
Senescent and Quiescent cells both
both exist in the G0/G1 phase of the cell cycle.
Method used to determine the life span of cells in culture
Hayflick and Moorhead's experiment to determine whether cells grown in culture have a finite life span
They apparently do.
Life history of mitotic cells in culture, as originally described by Hayflick and Moorhead
Phenotype of a senescent cell population
binding site on the antigen
can look different and can be so old that they get targeted by the immune system
Possible causes for senescent cells
Chronological vs. replicative aging
Damage accumulation in yeast aging
Shared aging in yeast cells
accumulation of rDNA circles
can prevent a cell from dividing
The mt is always producing
reactive oxygen species which damages the cell
Carbon metabolism and yeast aging
Is aging the consequences of unrepaired DNA damage?
Transgenic mice engineered to express
a mutant DNA helicase show premature aging
Hayflick Factors" Record the Proliferative History of Cells and Tissues
The proposed p53 protein mechanism of cell senescence
The mitotic clock theory of cell senescence
In somatic cells, telomeres shorten after each cell division
Telomeres serve as caps at the ends of linear chromosomes. They following are true
The structure of a portion of telomerase
A demonstration that yeast cells control the length of their telomeres
Age predicts telomere length in zebra finches
Germ line and early embryonic cells have endogenous telomerase activity.
Somatic cells with or without telomerase, telomeres shorten to about 4-7 kilobases
whereupon they become senescent.
Telomere shortening and senescence can be prevented by introducing telomerase.
[ectopic telomerase] However telomerase does not prevent senescence induced by
Telomere-dependent senescence can be prevented or delayed by inactivating p53
and/or RB. However telomeres continue to shorten until cells reach crisis. Cells in crisis
must activate a telomere stabilization mechanism in order to survive.
Telomeres protect chromosomes from fusion events
fusion occurs in a state of crisis
Could telomerase be used as a therapeutic agent?
Stress causes telomere shortening
Cellular Senescence: Balancing Cancer and Aging
Senescence of Stem Cells and Committed Cells
is caused by a variety of loss-of-function
mutations in a gene coding for a member of the RecQ helicase
family[WRN]. WRN helicase interacts with a wide variety of proteins
suggesting roles in DNA replication,recombination and apoptosis. Its main function blocks re-initiation of DNA replication at stalled
replication forks. This triggers sensitivity to DNA damaging agents and a
frequency of deletion mutations. The result is a very limited ability for
cells to divide. In cell culture WRN fibroblasts can double about 20 times
while normal fibroblasts can double 40 to 100 times. WS cells can be
induced to re-initiate DNA replication by the insertion of a telomerase
gene. BUT Why would this mutation result in the Werner Syndrome phenotype?
The Werner phenotype
Short stature, accelerated atherosclerosis, ateriosclerosis, graying of the hair, type II diabetes, cataracts, osteoporosis, and thymic atrophy.
a loop structure,
the telosome/shelterin complex ,
containing a six protein complex.
During DNA replication the presence
of WRN enables the efficient
replication of telomeric DNA by
Werner's Syndrome [WS] is a
premature aging syndrome
that is caused by a single gene mutation of WRN. The mutation results in a rapid onset of cellular senescence.
A Werner's Syndrome patient
Defects in a nuclear lamin can cause a rare class
of premature aging disorders called progeria
Some chromatin within a cell is normally associated with the nuclear lamina. Is this chromatin generally
Biosynthesis and maturation of lamin A, C and of progerin
Cell senescence in laminopathies results from several and combined factors.
Strategies designed for HGPS treatment
The central role of mitochondria in aging
A Schematic Model of ROS Generation in the Mitochondria
Potential Targets of ROS within Cells that May Determine the Rate of Aging
Reactive oxygen species can lead
to the cellular accumulation of damaged biomolecules at all levels of cellular organization
Steps in the generation of the superoxide radical, •O-2, in mitochondria
Reduction of the superoxide radical to water in mitochondria
Cytosolic reduction of the superoxide ion to water
If you increase catalase
you increase the life span of an animal because you can deal with the radical damage
Changing levels of SOD and catalase can influence lifespan F
Changing levels of SOD and catalase can influence
Life span decreases as
food intake increases. And Fecundity [reproductive capacity] increases as food intake increases.
The effects of various interventions on human life expectancy
Electron transport via NADH generates NAD+ in mitochondria a
and may decline with age
Various uses of NAD+ for canonical redox and NAD+-‐consuming
Gene silencing by the Sir2 protein
If you increase the activity of Sir2
you can increase the life span
Some gene mutations in drosophila that extend life span
The Sir-2 gene is a histone and other protein de-acetylase
It acts to silence genes at specific loci leading to increased life span. [Yeasts and nematodes] [Turns off aging genes] Sir-2 requires NAD+. Gene silencing can also be mediated by small [silencing] RNAs
A proposed mechanism that links energy metabolism in S. cerevisiae to an extended life span
Are there human Sir proteins? Can they extend the lifespan of human cells?
Sirtuins may be invoved with
Sirtuins [SIRT1-7] are a family of seven proteins linked to aging, metabolism and stress tolerance
They are considered anti-aging proteins. Increasing their activity retards aging.
They catalyze either ATP-dependent deacetylation or ADP-ribosylation. Both mechanisms require the cleavage of NAD to form nicotinamide. SIRT1 regulates important aspects of mitochondria. During caloric restriction or by
activation by certain small molecules, SIRT1 deacetylates PGC-ά which promotes biogenesis of mitochondria, improving mitochondrial function and decreasing the rate of ROS formation. Increased surface area of mitochondria lowers the hyper-polarization of the mitochondrial membrane that occurs when electrons get stalled along the electron transport chain which causes protons to be pumped to the cytoplasm leading to ROS.
Pleiotropic effects of SIRT1 on age-related diseases
Properties and functions of mammalian sirtuins
They have diversified in our own bodies as opposed to others
Sirtuin activating compounds (STACs) that extend lifespan and/or healthspan
Outline of sirtuin activating compound (STAC) effects on aging and age‐related diseases
Conserved pro‐aging pathways and their
The two mTOR complexes have distinct constituent proteins and regulate different downstream processes
Mammalian target of rapamycin (mTOR)
controls protein synthesis.
The two mTOR complexes have
distinct constituent proteins and regulate different downstream processes
transcription factors that activate transcription of genes that inhibit cell proliferation & induce cell death
Tissue heterogeneity and stem-cell functionality for homeostasis and repair
Influences on stem-cell functionality
Aging of stem-cell functionality
Cyclins and corresponding phases
is a common enzyme found in nearly all living organisms exposed to oxygen (such as vegetables, fruit or animals). It catalyzes the decomposition of hydrogen peroxide to water and oxygen. It is a very important enzyme in protecting the cell from oxidative damage by reactive oxygen species (ROS).
The key defining aspect of a stem cell
is that it is undifferentiated and can continuously divide.
Stem cells maintain their popula5on and give rise to differentiated tissues
are cells defined by their ability to self renew and differentiate into mature cell types.
During the blastocycst phase
cells are pluripotent but cannot give rise to the extra embryonic tissues
You started as a
Chromatin state changes
between stem and differentiated cell types
Nuclear lamina structure and stem cell
The chromatins are in a more open state in stem cells
is lamina associated domains
Open chromatin in stem cells
Mechanisms suppressing stem cell differentiation
Mechanisms suppressing stem cell
moving one cell from a signaling source
Maintenance and differentiation of embryonic stem cells
LIF and BMP
are important in keeping the pluripotentcy
Differentiation initiates chromatin state change
Stem cell niches
give stem cells the necessary environments to keep their "stemness"
The partner cell of the stem cell
is usually differentiated
The three types of stem cell niches are
simple niches, complex niches and storage niches
General mechanisms of fate determination
Overview of adult stem cells
The Two Daughters of a Stem Cell Do Not Always Have to Become Different
Niche regulation of stem cell renewal and differentiation
The Hub keeps a cell a stem cell via
adhesion and signaling factors
The hematopoietic stem cell niche
The key defining aspect of a stem cell
is that it is undifferentiated and can continuously divide.
Stem Cells Depend on Contact Signals From Stromal
Bone Marrow Contains Multipotent Hematopoietic Stem Cells, Able to Give Rise to All Classes of Blood
In transient amplifying population
when hemo stem cells go from slow dividing to fast dividing
are the high-affinity cell surface receptors for many polypeptide growth factors, cytokines, and hormones. Of the 90 unique tyrosine kinase genes identified in the human genome, 58 encode receptor tyrosine kinase proteins
Activation of ABL Kinase
The Philadelphia chromosome causes an activated form of Abl to be produced
ABl kinase exists downstream
of the kit pathway
signaling is plays important role in a number of physiological processes including erythropoiesis, lymphopoiesis, mast cell development and function, megakaryopoiesis, gametogenesis and melanogenesis.
The cell cycle in hematopoietic stem cells
Loss of quiescence results in loss of function in
adult stem cells
Bone marrow transplants repopulate all blood
Why do people go bald or gray?
fast growing cells
Hair follicle stem cells can be used to
grow new hair
Wnt signaling in the intes5nal epithelium
The Lining of the Small Intes5ne Is Con5nually
Renewed Through Cell Proliferation in the Crypts
The canonical Wnt signaling pathway
Colon with cancer vs. without
The muscle stem cell (satellite cell) niche
Some Myoblasts Persist as Quiescent Stem Cells
in the Adult
are muscle stem cells
Myoblasts Fuse to Form New Skeletal Muscle
Symmetric and asymmetric division of
Loss of myostatin has severe effects on muscle
Myostatin, a TGFβ ligand, inhibits muscle stem cell activation and the formation of new muscle
Plants have stem cell too!
Naturally occurring Myostatin mutations
Genomic engineering trout for enhanced muscle
Embryonic Stem (ES) Cells Can Generate Any
Part of the Body
ES and iPS Cells Can Be Guided to Generate Specific
Adult Cell Types and Even Whole Organs
Cloned Xenopus laevis frogs using
albinism as a marker
Cloning of mammals by nuclear
Do cloned animals prematurely age?
Serial cloning of mice does not reveal
shortening of telomeres over subsequent generation
Fibroblasts Can Be Reprogrammed to Create Induced
Pluripotent Stem Cells (iPS Cells)
The Different Cell Types of a Multicellular Organism Contain the Same DNA
Experimental method for the discovery of induced pluripotent stem cells
ES and iPS Cells Are Useful
for Drug Discovery and
Analysis of Disease
-inhibits growth and proliferation of myoblasts (produces muscle cells
Reprogramming Involves a Massive Upheaval of the Gene Control System
Reprogramming Involves a Massive Upheaval of the Gene Control System 2
An Experimental Manipulation of Factors that Modify Chromatin Can Increase Reprogramming Efficiencies
Timeline of nuclear reprogramming
Poly (ADP-ribose) polymerase (PARP)
is a family of proteins involved in a number of cellular processes involving mainly DNA repair and programmed cell death.
PARP can be activated in cells experiencing stress and/or DNA damage
Activated PARP can deplete the ATP of a cell in an attempt to repair the damaged DNA. ATP depletion in a cell leads to lysis and cell death (necrosis). PARP also has the ability to induce programmed cell death, via the production of PAR, which stimulates mitochondria to release AIF. This mechanism appears to be caspase-independent. Cleavage of Parp, by enzymes such as caspases or cathepsins, typically inactivate Parp. The size of the cleavage fragments can give insight into which enzyme was responsible for the cleavage, and can be useful in determining which cell death pathway has been activated.
The ABL1 proto-oncogene
encodes a cytoplasmic and nuclear protein tyrosine kinase that has been implicated in processes of cell differentiation, cell division, cell adhesion, and stress response. Activity of ABL1 protein is negatively regulated by its SH3 domain, and deletion of the SH3 domain turns ABL1 into an oncogene.