eukaryotic transcription regulation

Question 1

why is gene expression regulated?

eukaryotes

Answer 1

as genes encode proteins which dictate cell function
regulated by differential gene expression due to the combination of different transcription factors

Question 2

how is gene expression regulated?

eukaryotes

Answer 2

cells have distinct sets of transcription regulators; some of these regulators work to increase transcription whereas other prevent or suppress it, so that only a small fraction of the genes in a cell are expressed

Question 3

potential points for gene expression regulation

eukaryotes

Answer 3

remodelling of chromatin to increase promoter accessibility and therefore transcription
pre-mRNA synthesis
pre-mRNA splicing
transport of mRNA from the nucleus to the cytoplasm
mRNA stability
protein synthesis - control of translation
post-translational modification
protein degradation

Question 4

how is transcription regulated?

eukaryotes

Answer 4

basal transcription factors bind the core DNA promoter (starting with TFIID) to recruit RNA polymerase, the level of transcription is determined by the promoter strength
transcriptional activator or repressor proteins bind to the promoter to enhanve or repress transcription levels

Question 5

summary of transcription regulation

eukaryotes

Answer 5

TFIID binds at promoter TATA box
transcription factors also bind
recruitment of RNA polymerase
more transcription factors bind
initiation of transcription

Question 6

transcription factors, activators and repressors

eukaryotes

Answer 6

a long stretch of DNA lies between the activator binding site and the transcription complex
DNA bending can bring an activator protein, bound to an enhancer element far from the promoter, into contact with the transcription complex

Question 7

enhancer

transcriptional factors, activators and repressors

Answer 7

a cluster of various transcription factor binding sites

Question 8

transcriptional activators

eukaryotes

Answer 8

have multiple protein domains

Question 9

DNA binding domain

transcriptional activators

Answer 9

sequence-specific recognition
brings the transcription-activation domain into the vicinity of the promoter

Question 10

regulatory domain

transcriptional activators

Answer 10

dimerisation, nuclear transport and autoinhibition
cooperativity in DNA binding

Question 11

activation domain

transcriptional activators

Answer 11

recruitment
transctriptional activation

Question 12

collaborators

transcriptional activators

Answer 12

chromatin remodelling enzymes
coactivators/corepressors
general transcriptional machinery

Question 13

homo- and heter- dimerisation

eukaryotes

Answer 13

can recognise different DNA sequences
homodimer 1 - ‘weak’ activator
homodimer 2 - ‘weak’ repressor
1+2 heterodimer - ‘strong’ activator

Question 14

cooperativity

eukaryotes

Answer 14

the arrangement of transcription factors binding sites so that two different transcription factors can interact to stabilise each other’s binding to DNA

Question 15

combinatorial control

eukaryotes

Answer 15

multiple regulatory factors (transcription factors, coactivators, repressors) work together in various combinations to control the activation or repression of genes

Question 16

drought-sensitive transcription factor

combinatorial control

Answer 16

drought (activator) > transcription of regulatory protein > binds to stress response element > transcription of genes A,B and C > different proteins > stress response