Bacterial Gene Regulation

Gene regulation

process used to control the timing, location, and amount in which genes are expressed

structural genes

encode protein that are used in metabolism or biosynthesis or that play a structural role in the cell

Regulatory genes

regulatory genes interact with other DNA sequences and affect the transcription or translation of those sequences

Constitutive

encode essential cellular functions and are expressed continually

regulatory elements

affect the expression of DNA sequences that they are physically linked to it

positive control

stimulation of gene expression

negative control

inhibition of gene expression

levels of gene regulation

regulated through the alteration of DNA or chromatin structure

determines which sequences are available for transcription of the rate at which sequences are transcribes

example: DNA methylation

level of transcription

change in transcription rate to prevent waste of protein machinery

mRNA processing (eukaryotes)

-movement from nucleus to cytoplasm

• rate of translation

  • example: 5’ cap, poly-a tail `

translation

availability of necessary components

protein modification

modifications affect protein stability and protein activity

domain

responsible for binding to DNA and forming hydrogen bonds with DNA

~60-90 amino acids

interact with sugar phosphate backbone

motif

simple structure that fits into the major groove of DNA

in the binding domain

transiently bind

operon

group of bacterial structural genes

promoter

additional sequences that control transcription

structural genes

code for enzymes

enzymes used in biochemical pathway to convert reactants to products

True or false a regulator protein binds to an operator

true

operator

DNA sequence in an operon

overlaps 3’ end of promoter and can overlap with 5’ end of structural gene

negative control

regulated by a repressor protein

positive control

regulated by an activator protein

negative inducible operon

encodes an active repressor protein → binds to the operator

rna polymerase unable to bind to the promoter

control proteins that carry out degenerative processes

turning transcription on

• inducer binds to repressor protein

• shape of repressor changes when inducer binds

  • allosteric change

turning off transcription

• corepressor binds to repressor protein

  • product from biochemical pathway

    • repressor bind to operator

catabolite repression: genes that participate in the metabolism of other sugars

turned off when glucose is present

catabolite active protein

located within or slightly upstream of the promoter of the lac genes

acts as positive control

true r false rna polymerase does not bind efficiently unless CAP is bound first

true

true or false cap forms a complex with camp before binding to dna

true

tru or false the trp operon leads to the synthesis of lactase

false it leads to the synthesis of tryptophan

trp operon

negative repressible operon

trpR regulator gene codes for inactive repressor

attenuation

transcription site begins at the transcription start site

termination occurs before structural genes

5’ UTR with four complementary regions

folds into secondary structures based on complementarity

attenuator

secondary structure that forms in the 5’ UTR

region 3 and 4 pair

causes the premature termination of transcription

antiterminator

protein or DNA sequence that prevents the termination of transcription

antitermination

region 1 has two UGG codons for tryptophan

rna polymerase trancribes region 1

ribosome stalls at trp condos preventing 1 and 2 from pairing

region 2 not covered→ region 2 and 3 pair