Chromatin Remodelling And Repression

Question 1

What are the readers in the histone code

Answer 1

Bromodomains
Chromodomains phD

It’s proteins which read the post translational modifications

Question 2

Other than acetylation Nd methylation. Which other way can chromatin be remodelled

Answer 2

Atp dependant chromatin remodelling

Question 3

What type of ATPase do all atp dep remodelling complexes have

Answer 3

Snf 2

Question 4

There are 4 subfamilies of the super family 2 atp dep remodelling complexes. What are they

Answer 4

Snf2/swi2

ISWI

Chd/mi2

Ino80

Question 5

What characterises swi2/snf2 remodel complex

Answer 5

A bromodomain and a snf2 ATPase

Question 6

What characterises chd/ mi2 remodeller

Answer 6

Chromodomain and a dna binding domain

And the snf 2 ATPase domain

Question 7

What characterises the ino 80 complex

Answer 7

A split ATPase domain

Question 8

What do remodellers like chd mi2 use ATPase hydrolysis for

Answer 8

Sliding, unwrapping, spacing, evicting nucleosomes

And

Histone variant exchanges

Question 9

What does swi2/snf2 remodellers do using the snf2 ATPase

Answer 9

Induce torsions in dna and change the position of dna around nucleosome

Question 10

What do atp remodelling complexes work with

Answer 10

Hats like tra1 which is bound to gcn5 activator

Question 11

How is bromodomain of snf2 attracted to tra1 HAT

Answer 11

Because tra1 has acetylated lsyines around it and the bromodomain of snf2 recognises this

Question 12

What does hat and atp complexes cooperation do

Answer 12

Allow pic recruitment

Question 13

What genes does snf2 in yeast regulate

Answer 13

Genes at end of mitosis

Question 14

What role does human snf2 have in cell cycle regulation

Answer 14

Interacts with cyclin E and Rb (tumour repressor) repressor

Question 15

What would mutation in snf2 in humans cause

Answer 15

Tumours

Snf2 is used for tumour suppression

Question 16

Snf2 is important for transcription factor expression. Give examples

Answer 16

HSF, myoD, glucocorticoid and retinoids receptors

Question 17

Can atp dep remodelling also cause repression of txn

Answer 17

Yes

Question 18

Which enzymes are important in repression

Answer 18

HDACs and histone methylases HKMT via lys 9 and 28

Question 19

How do HDACs repress

Answer 19

Hypoacetylate lysine residues on n terminal tail via hydrolysis

Adds positive charge back to lysine

Dna will tightly bind to nucleosomes

Question 20

Just like hats are co activators with snf2, what are HDACs

Answer 20

Co repressors

Question 21

What are class 1,2 and 4 HDACs dependant on

Answer 21

Zinc

Question 22

What is class 3 sir 2 HDACs dependant on

Answer 22

Nad

Question 23

Which repressor gene that has a dna binding domain forms a complex with HDACs for co repression

Answer 23

Ume6 gene

Question 24

Which complex is formed by the corepressors ume6 and rpd3 HDAC

Answer 24

Sin3

Question 25

What genes do sin3 repress

Answer 25

Meiosis genes

Question 26

Which atp dependant remodeller is a repressor

Answer 26

NuRD - mi2/chd family

Question 27

How does nuRD repress

Answer 27

Decreases spacing of nucleosomes fotming CLOSED CHROMATIN

Question 28

Does the nuRD repressor also have a HDAC

Answer 28

Yes

Question 29

Histone lysine methyl transferases hkmt are repressing if at lys 9 and 28, is this found in heterochromatin

Answer 29

Yes

Question 30

Aswell as hkmt at 9 and 28, what other properties does hetereochromatin have

Answer 30

Hypoacetylation via HDACs And Association with silencing factors

Question 31

How is H3 lys 9me produced in heterochromstin

Answer 31

Lys 9 is deacetylated via HDACs Then a hkmt methylated the lysine 9 (K9) This is recognised by chromodomain proteins HP1 of tri and di methyl groups HP1 will form compact nucleosomes and recruit other repressors

Question 32

What is HP1

Answer 32

Heterochromatin protein 1 with a chromodomain

Question 33

Which hkmt methylates H3 lysine 9

Answer 33

Suvar 39

Question 34

Which reporter gene is used in a reporter silencing assay to analyse heterochromatin

Answer 34

Ade6, when expressed it turns white

Question 35

What happens when ade6 is placed in heterochromstin region

Answer 35

Switched off and adenine intermediate turns red

Question 36

Which non coding rna is switched on during development to inactivate an X

Answer 36

Xist

Question 37

Which hkmt is attracted when xist is switched on for repression

Answer 37

H3k27 methylases

Question 38

What does hkmt h3k27 do when recruited by xist to repress x

Answer 38

Recruit other silencing factors to inactivate the x