Lecture 3 - Histones, nucleosomes and chromatin structure

Question 1

the template strand of DNA is not …….. as it is packaged in a protein complex called……

Answer 1

naked

chromatin

Question 2

what is the basic function of chromatin?

Answer 2

to compact and shrink down the length of DNA (so it can fit in one nucleus)

Question 3

chromatin is composed primarily of small basic proteins called……..

Answer 3

histones

Question 4

what are the 2 types of histones?

Answer 4

core and linker

Question 5

the N terminal tail of core histones is highly basic, rich in which 2 residues?

Answer 5

lysine and arginine

Question 6

the globular domain of a core histone contains what type of helices?

Answer 6

alpha

Question 7

core histones form repeating units called what?

Answer 7

nucleosomes

Question 8

how many base pairs of DNA are in a nucleosome?

Answer 8

around 147 bp

Question 9

how many times are base pairs of DNA wrapped around an octamer of histone proteins?

Answer 9

twice

Question 10

an octamer of histone proteins contains a central tetramer and 2 x flanking dimers? name them all

Answer 10

H3-H4 tetramer
2 x dimers of H2A-H2B

Question 11

H…… is a linker histone?

Answer 11

H1

Question 12

where do linker histones bind to?

Answer 12

the DNA between nucleosomes

Question 13

evidence suggests that a regularly folded …..nM fibre is unlikely to exist in vivo

Answer 13

30 nM

Question 14

there is evidence that chromatin can…… transcription

Answer 14

inhibit

Question 15

the H4 gene is under the…… promoter in s.cerevisiae

Answer 15

GAL4

Question 16

true or false, chromatin structure is dynamic?

Answer 16

true

Question 17

all conventiional histones, except……. have variants

Answer 17

H4

Question 18

histone variants confer novel……. and functional properties of the ……. which affect the chromatin dynamics

Answer 18

novel structural

nucleosome

Question 19

Histones are subjected to a variety of post translational modifications which play a key role in controlling gene expression. Name 4 modifications

Answer 19

acetylation, methlyation, ubiquitylation, phosphorylation

Question 20

histone lysine acetylation is mediated by which group of enzymes?

and is readily reversible by which group of enzymes?

Answer 20

mediated by HATs

reversed by HDACs

Question 21

which 2 families (large multisubunit complexes) are HATs known to function in?

Answer 21

GNAT and MYST

Question 22

HATs are recruited to specific promoters by what?

Answer 22

by activators

Question 23

name a specific HAT subunit that interacts with the activator TRRAP

Answer 23

Tra1

Question 24

acetylation can reduce the …….. charged …….terminals of histones which helps to keep them compact

Answer 24

positively

N

Question 25

acetylation can direct the recruitment of which domain proteins?

Answer 25

bromodomain

Question 26

what do bromodomain proteins promote?

Answer 26

transcription

Question 27

give 2 examples of bromodomain proteins which bind acetylated H4

Answer 27

Bdf1 TAFII250

Question 28

which 2 residue can histone METHYLATION occur on? which is the more common residue?

Answer 28

lysine and arginine (lysine most common)

Question 29

lysines can be methylated by which domain proteins, containing SETs)? do demethylases exist? does methylation affect charge of chromatin?

Answer 29

by HKMTs yes no

Question 30

increased H3 Lys9 and Lys27 methylation is associated with what?

Answer 30

repression

Question 31

H3 Lys4 and Lys36 are associated with what?

Answer 31

activation

Question 32

Which histone can direct the formation of the 30 nm fibre in vitro?

Answer 32

H1

Question 33

In which region are histones subjected to extensive post-translational modification?

Answer 33

in their N terminal tails