7 Control Sites in the DNA -> RNA -> Protein Scheme
1. Chromosomal Placement - gene located in eu- or heterochromatin
2. Transcriptional - DOMINANT control mechanism
3. RNA Processing - which RNA's mature
4. RNA Transport/Localization - which mRNA's leave nucleus and to where
5. Translational - fine tuning at ribosome
6. Turnover of mRNA - the half-life of certain mRNA's
7. Protein Activity - post-translational activity, folding, turnover, compartmentalization
contains protein coding information and untranslated 5' and 3' sequences
Core Promoter Elements: contact components of RNA polymerase.
Enhancer/Silencer Elements: bind specific transcriptional factors that alter the rate of transcriptional initiation or elongation.
Expression unit consisting of collection of genes (that produce proteins with complementary functions), the operator, and promoter (all the genes within the operator are regulated collectively).
3 Genes of the Lac Operon
1. galactoside permease (lacY) -- transporter
2. beta-galactosidase (lacZ) -- catabolic enzyme
3. galactoside transacetylase (lacA)
1. the breakdown of Lactose into Glucose + Galactose
2. the formation of Allolactose from Lactose (Impt for regulation)
CRP (cyclic AMP receptor protein)
Binds to the CRP site on the Lac Operon with cAMP as a cofactor and activates transcription when glucose is LOW. Low glucose = high cAMP.
2 Mechanisms of Trp Operon Regulation
1. Repression by Trp Repressor -- binds to Operator in presence of Tryptophan
2. Transcriptional attenuation in presence of Tryptophan