Transcription regulation #2

Question 1

Co-activators/Co-repressors

Answer 1

help with regulate transcription but do not have DNA-binding abilities themselves

Question 2

Types of eukaryotic gene expression regulation

Answer 2

chromatin modification
~ histone acylation
~ nucleosome-remodelling complexes
DNA methylation

Question 3

Histone acetylation

Answer 3

~ modification at lysine residue in N-terminal tail
~ hypoacetylation
~ hyperacetylation
~ acetyl groups can also recruit proteins using bromodomain proteins

Question 4

Hypoacetylation

Answer 4

strong internucleosomal interactions - histone tail contains DNA wrapping

Question 5

Hyperacetylation

Answer 5

weak internucleosomal interactions - histone tails do not constraint DNA wrapping = accessible for transcription factors

Question 6

Chromatin remodelling complexes

Answer 6

~ uses ATP to move the histone octamer
~ can be recruited:
a) sequences-specifically
b) histone modification

Question 7

DNA methylation

Answer 7

~ transcriptionally active genes = lower levels of DNA methylation
~ methylation affects chromatin structure
~ methyl groups (on DNA or histone tails) can recruit methyl-binding proteins which recruit other proteins that modify chromatin

Question 8

Mediator complex

Answer 8

~ transcription factors required by DNA pol II

~ contains 20 proteins

Question 9

Recruitment of mediator complex

Answer 9

~ in absence of mitogens, ELK1 binds to serum response factor (SRF)
~ mitogen-activated signal transduction pathways phosphorylate ELK1
~ phosphorylate ELK1 recruits mediator complex, promoting transcription

Question 10

Yeats + GAL genes

Answer 10

~ GAL1, GAL7 + GAL10 encode enzymes that metabolise galactose
~ absence of galactose = no transcription
~ galactose present + no glucose = transcription
~ genes are near each other but are NOT an operon

Question 11

Gal4

Answer 11

regulatory proteins that binds to UAS(G) and activated transcription
no galactose = Gal80 binds to Gal4
galactose present = Gal3 binds to Gal80, Gal4 recruits SAGA and Mediator = transcription

Question 12

Ume6

Answer 12

~ transcriptional repressor that repossess to nutritional cues
Lots of N + C = Ume6 binds to DNA and recruits Rpd3 + Isw2
No N + C = Ume6 is phosphorylated and Ime1 is recruited

Question 13

Promoter proximal pausing

Answer 13

RNA pol II stalls after 30-50bp have been transcribed
~ promoted by negative elongation factors
e.g. Drosophila Hsp70

Question 14

hsp70 transcription (no heat)

Answer 14

GAGA transcription factor recruits NURF
~ NURF alters chromatin structure, exposing control elements
~ negative elongation factors prevent phosphorylation of Rpb1

Question 15

Name two negative elongation factors for hsp70 transcription

Answer 15

NELF

DSIF

Question 16

hsp70 transcription (heat)

Answer 16

~ Hsf protein forms a trimer
~ trimer binds to HSE sequence
~ trimer interacts with Mediator and recruits a kinase
~ CTD is phosphorylated, relieving the pausing