Trigger 8: Histone modification

Question 1

chromatin compaction

Answer 1

influences activity of DNA in transcription

Question 2

DNA is only transcribed and expressed in

Answer 2

euchromatin form

- involves a write, reader and eraser

Question 3

when the gene is switched on

Answer 3

• active (open) chromatin
• unmethylated cytosine
• acetylated histones

Question 4

when the gene is switched off

Answer 4

• silent (condensed) chromatin
• methylated cytosines
• deactivated histones

Question 5

histones can be

Answer 5

• acetylated
• deactivated
• phosphorylated
• methylated

Question 6

histone core is made up of how many histone proteins

Answer 6

4

Question 7

which histone proteins make up histone core

Answer 7

H2A H2B H3 H4

Question 8

histone tails provide site for

Answer 8

covalent modification:

acetylation, methylation, phosphorylation etcs

Question 9

modifications to histone tail determien

Answer 9

the interaction of histone with other proteins, which may in turn regulate chromatin structure and therefore transcription

Question 10

histone code

Answer 10

can occur in various combinations- which have a specific meaning

• complex is read by specific protein complexes which contain proteins which recognise specific histone marks and binds to them

Question 11

Acetylation of histones are catalysed which enzyme

Answer 11

Histone acetyltransferase (HAT)

Question 12

deactetylation of histone s is catalysed by

Answer 12

histone deactylase (HDAC)

Question 13

acetylation….

Answer 13

-removes +ve charge of the histone tail, reducing affinity for -ve charged phosphates of DNA

reduces affinity of tail for adjacent nucleosomes- relaxing the chromatin structure

Question 14

HATs

Answer 14

add acetyl to histones- allowing transcription

Question 15

HDACs

Answer 15

remove acetyl from histones- stopping transcription

Question 16

adding acetyl causes…

Answer 16

euchromatin protein structure

Question 17

removing acetyl causes

Answer 17

heterochromatin structure

Question 18

acetylation overall increases

Answer 18

access of TFs to DNA through structural changes

Question 19

which domain found in TFs and HATs allows for preferential recognition of histone tails when they are acetylated

Answer 19

bromodomain

Question 20

methylation of histone tails

Answer 20

recruits silencing or regulatory proteins that bind to methylated histones

Question 21

which domain interacts with methylated histone tails

Answer 21

chromodomain

Question 22

methylation

Answer 22

introduction of methyl functional group to LYSINE OR ARGININE of the histone tail

Question 23

which amino acids in histone tail are methylated

Answer 23

lysine or arigine

Question 24

which enzyme catalyses methylation reactions on histones

Answer 24

histone methyltransferase

Question 25

how many times can Arg be methylated

Answer 25

1 or 2

Question 26

how many times can Lys be methylated

Answer 26

1,2,3

Question 27

H3k27ac is

Answer 27

an important enhancer mark that ca distinguish between active and poised enhancer elements

Question 28

H3K4 is

Answer 28

activated whether it is methylated or acetylated

Question 29

H3K4me3 is the

Answer 29

methylation state associated with transcriptional start sites of actively transcribed genes

Question 30

H3K9ac

Answer 30

activation

Question 31

name three active markers

Answer 31

H3K27ac H3K4 H3K9ac

Question 32

repressive enhancers

Answer 32

when H3K27 is trimethylated- highly associated with inactive gene promotors

Question 33

H3K9

Answer 33

silenced

Question 34

phosphorylation of histone tails

Answer 34

activation of transcription