19.2: Control Of Transcription

promoter

gene sequence near transcription start site that attracts RNA polymerase

TATA box

consists of 7 nucleotides of sequence T A T A…

located upstream of the transcription start site

helps position RNA polymerase ii correctly for it to start transcribing the gene at the right location

enhancer

acts as binding sites for transcription factors and are responsible for increasing transcription rates

the transcription factors can interact with the promoter to activate it

DNA physically loops to bring enhancer close to promoter (increasing gene expression)

cis acting elements

DNA sequences located on the same DNA molecule as the gene they control 

promoter and enhancer

what are examples of cis acting elements?

transcription factor

a protein whose DNA sequence-specific binding to a cis-control element regulates the timing, location, or level of a particular gene’s transcription

basal factors

bind to specific DNA sequences in the promoter 

interacts with RNA polymerase to allow it to bind and begin transcription

tata box binding protein

example of basal factor

mediator

bridge between pol ii complex at the promoter and the activator OR repressor proteins bound at the enhancer

activator 

a type of transcription factor that binds to specific DNA sequences within enhancer elements and increases the level of transcription from a nearby promoter

RNA polymerase and coactivators

activator recruits

coactivator

proteins that open chromatin structure to allow gene transcription

closed chromatin

promoter DNA that is covered with blank is inaccessible to basal factors

dna binding and activation

what are the two structural domains within the activator protein?

zinc fingers and helix turn helix

what are the two DNA binding domains?

dimerization domain

domain that enables activator polypeptides to interact with other copies of the same polypeptide or with other transcription factors

homodimer

protein complexes consisting of 2 identical polypeptidees

heterodimer

protein complexes consisting of 2 different polypeptides 

repressor

eukaryotic transcription factors that bind specific DNA sites near a gene and prevent transcription

recruit corepressor proteins to enhancers

eukaryotic repressors generally

similar

repressors have a blank structure to activators

repressor structure

dna binding motifs and repression domains

indirect repressor

a protein that interferes with the function of an activator without necessarily binding DNA

acetylation and methylation

for transcription the most important modifications are 

histone acetyltransferases (HATs)

enzymes that acetylate histone tail lysines resulting in open chromatin

histone methyltransferases (HMTs)

enzymes that methylate histone tail lysines and arginines and can either bind factors that open or close chromatin

histone deacetylases

enzyme that removes acetyl groups from histone tail lysines and closes chromatin

histone demethylases

enzymes that remove methyl groups from histone tail lysines which affect chromatin structure

insulator

DNA elements that organize chromatin into loops called topically associated domains

same TAD

an enhancer and promoter can only interact if they are in the