Eukaryotic control of gene expression

Question 1

Activators and repressors

Answer 1

Bind DNA and activate transcription

Activators bind enhancer regions
Repressors bind silencer regions

Question 2

DNA looping

Answer 2

Brings remote enhancer/repressor elements into contact with promoter/polymerase

Occurs via mediator complex
DNA bending proteins and loop stabilising proteins (cohesin)

Question 3

Enhancers

Answer 3

Interact with and stabilise TFIID and RNA pol2 via mediator

Can influence local chromatin structure

Interact with activators and co-activators

Question 4

Mediator complex

Answer 4

Made up of co-activators

PIC interacts with chromatin modelling factors via mediator

Question 5

Combinatorial control

Answer 5

Activators can activate a number of different genes in different combinations

Question 6

Insulators

Answer 6

Control action of activators
Block genes from indiscriminate activation/repression
Can block spread of chromatin modifications

Question 7

Activation of gene structure

Answer 7

Chromatin altered to allow expression of genes

Requires transcriptional activators

Question 8

Chromatin

Answer 8

Negatively charged DNA associated with positively charged DNA compaction proteins

Packages DNA into the nucleus
Regulates gene expression
Prevents DNA damage and regulates repair

Question 9

Histones

Answer 9

H2A, H2B, H3 and H4

Each core histone has an N-terminal tail that extends out of the coils

Interact with other nucleosomes for compaction

Can be chemically modified

Question 10

Histone gene suppression

Answer 10

High nucleosome density
High repressive methylation
Hypoacetylation

Question 11

Histone modification and remodelling

Answer 11

Chemical modification with histone acetylase
Remodelling with Chromatin remodelling complex

Both recruited by activators
Exposes promoter region

Question 12

H2A.X

Answer 12

Histone variant that replaces H2A often during damage

Has different modification sites on the tail

Question 13

SWI/SNF complex

Answer 13

ATP-dependent translocating component

ATP hydrolysis facilitates movement of histones along DNA

Question 14

Cohesin

Answer 14

Chromosome maintenance protein

Forms rings around DNA during replication and stabilises DNA loops (brings enhancer closer to promoter)

Question 15

Major control point for gene expression in eukaryotes

Answer 15

Altering local structure of DNA
Transcription initiation (most control)
RNA transcript processing
mRNA transport from nucleus to cytoplasm
mRNA degradation and turnover

Question 16

Archaeal histones

Answer 16

Highly homologous to eukaryotes
Usually do not have N terminal tails
Histones can homodimerize and spontaneously oligomerise

Question 17

Histone ubiquitination

Answer 17

H2A ubiquitination results in repression
H2B ubiquitination can activate or repress expression
Involves PRC1 ubiquitin ligase (E3)