14: Transcription regulation (prokaryotes)

at what points can you regulate genes

1. transcription initiation

2. post-transcription processing (splicing)

3. RNA stability

4. translational regulation

5. protein modification

6. protein transport

7. protein degradation

Core polymerase without sigma factor will initiate _

randomly

operons

clusters of co-regulated genes AND promotor and activating / repressor sites with related functions

(positive / negative) regulation is a molecular signal that causes dissociation of repressor from DNA inducing transcription

negative

(positive / negative) regulation is a molecular signal that causes binding of repressor from DNA inhibiting transcription

negative

_ help recruit sigma factors to enhance transcription

activators

(activators / repressors) bind to operators

repressors

(positive / negative) regulation is a molecular signal that causes dissociation of activator from DNA inhibiting transcription

positive

(positive / negative) regulation is a molecular signal that causes binding of activator from DNA incuding transcription

positive

negative regulation involves (activators / repressors)

repressors

positives regulation involves (activators / repressors)

activators

T or F. E. coli lac operon goes under both positive and negative regulation

true

function of lac Z

convert lactose → glucose + galactose or allolactose

_ enzyme converts lactose to allolactose

b-galactosidease

activators bind to the _

activator binding site

lac operon has # promoters

2

(activators / repressors) help bind sigma factors

activators

lacI is (activators / repressor)

repressor

in lac operon, there is / is not always some repression happening

is

allolactose binds to

repressor

lacZ takes place (inside / outside ) cytoplasm

inside

outline positive regulation of lac operon

1. starvation → cAMP

2. camp → CRP (cAMP receptor protein)

3. CRP binds to activator binding site

4. enhance gene expression (ON)

outline negative regulation of lac operon

1. lacI binds o2 and o1 to repress transcription

2. allolactose binds repressor

3. o1 is not repressed → ON

riboswitch

switches when responding to signals that creates poly U termination to terminate transcription

binding of mRNA riboswitch to TPP ligand results in conformational change and _

inhibits transcription

binding of mRNA riboswitch to _ ligand results in conformational change and inhibits transcription

TPP

when glucose is high, camp is (high / low)

low

when glucose is low, cAMP is (high / low)

high

glucose high / camp low + lactose absent =

no gene expression

glucose low / camp high + lactose absent =

no gene expression

glucose high / camp low + lactose present

low gene expression

glucose low / camp high + lactose absent =

no gene expression

when lactose is absent, lac repressor binds to _

operator (lacZ)

when lactose is present, lac repressor binds to _

allolactose

high levels of gene expression when glucose is __ and lactose is _

low, present

galactoside permease (lacY)

transports lactose from extracellular space into cytoplasm

allolactose releases _ from operator

lac repressor