G7 Flashcards

You may prefer our related Brainscape-certified flashcards:
1
Q

how many histone modicfications are possible and why?

A

280 billion possible modification

each combination of ptm on any number of AA’s of tail could cause a specific phenotype

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

where on a histone is usually modified?

A

the histone tailprotruding from the nucleosome often serves as a template for epigenetic
modifications.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what affect could modifications on histones have?

A

change binding affinities of nucleosome DNA
shift nucleosomes out of the way
change activation of transcription
recruit protein complexes that regulate chromatin state and gene activity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what types of modification can lysine residues go through and what enzymes do this

A

acetylation/deactylation HAT/HDAC
methylation/demethylation HMT/HDM
ubiquination/deubiquination7
ubiquitin ligase/protease

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what type of modifications can serine/thereonin go through and which enzymes does this?

A

phosphorylation/dephosphorylation by kinase phosphatase enzyme

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what type of modications can arginine go through and what enzymes catalyse this?

A

methylation (mono/di)
demethylation (citrullination)
PRMT/deiminase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what is the histone code hypothesis

A

transcription of genetic info encoded in DNA is in part regulted by chemical modification to hisstone proteins primarily on their unstructured ends.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what is HAT enzyme?

A

histone acetyl transferase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what does methylation cause at H3K4

A

= lysine residue methylation
transcriptional activation
demethylation = silencing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what does methyaltion at H3K9 cause?

A

silent heterochromatin = silencing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what does acetylation at H3K14 cause

A

transcriptional activation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what does methylation (mono/ditri) at H3K27 cause

A

transcriptional memory
mono = activation
di/tri= repression

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what does methylation at H3K36 cause

A

transcriptional elongation.

also lysine residue

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what does methylation at H3K79 and H4K20 cause

A

signalling G2/M arrest to allow DNA repair.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

how can histone modifying enzymes act?

A

intrinsically (on only single nucleosome) or extrinsically - affect nucleosome:nucleosome int4eractions.
can recruit other proteins to DNA via specific domains.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what does histone modification participate in the regualtion of?

A
many process; transcription
dna repar
chromatin assembly
silencing 
heterochromatin formation.
17
Q

how can chromatin enzymes be involved in cancer

A

mutations in enzymes = rubinstein-Taby syndrome and cancer
mutations in chromatin remodelling enzymes can cause cancer
mutations in epigentic effector proteins = rett syndrome cancer

18
Q

how can the papilloma virus lead to epidermal cacrinomas?

A

because contains genes that interact with methylation enzymes and histone modifcation enzymes

19
Q

what can diregualtion of gene expression in cancer cells lead to

A
- insensitivity to antigrowth signals
evasion of cell death (apoptosis)
immortalisation
impared DNA repair capacity
increased genomic instability
tissue invasion and metastasis (spread of cancer to other parts)
20
Q

what is knudsons two hit hypothesis of carcinogenesis?

A

one hit = epigentic, promoter methylation

subsequent events eliminating seconf copy of the gene such as a mutation

21
Q

what is an example of dergualtion of imprinting leading to cancer

A

Lol at the IFG2/GH19 locus leads to colon cancer

22
Q

how can age influence DNA methylation levels ?

A

Age - tendancy to become hypomethylated with age whereas certain CpG islands become hypermetylated

23
Q

how can diet influence dna methylation levels

A

diet - nutrition supplies methyl groups for DNA and histones - methylation via folate and methionine pathways as mammals cant synthesize these things.

24
Q

how can the environment influence DNA methylation levels

A

agents such as arsenic and cadmimum
arsenic - causes hypomethylation of ras gene
cadmium - induce global hypomethylation by inactivation DNMT1. associated with cancers

25
Q

Describe the process by which RB tumour repressor works

A

H3K9 methylation at promoters in early G1 phase. RB recruits deacetylases and methylases to repress the cyclin E gene
deacetylation and K9 trimethylation of histones results in condensed and transcriptionally repressed chromatin
loss of RB leads to depression of S phase inducing genes and proliferation

26
Q

what are chromatin remodellers?

A

large mulitsubunit complexes containing an enzymatic ATPase, core subinits and accessory subunits which load/slide or eject nucleosomes and are involved in cancers

27
Q

how are chromatin remodelling complexes affected in cancers

A

hSWI /SNF subunits are deregulated in cancers

28
Q

what is prader willi syndrome

A

deregulated genomic imprinting on chromsoome 15
obsessive hunger
mental defects
incomplete sexual development

29
Q

what is angelmans syndrome

A

loss of paternal genes on chromosome 15 due to imprinting, causes disease by maternal chromosome 15 deletion or inactivation
jerky movemetns
developmenntal dissability

30
Q

what is rubinstein taby syndrome

A

make half the normal amount of CREB gene invovled in growth
short stature
broad thumbs and toes

31
Q

what is rett syndrome

A

caused by mutations in x chromosome gene involved in epigenetic regulation
effects nearly always females
small hands and feet and decelerated head growth
jerky movements
mental retardation

32
Q

what is angelamns to prader willi

A

sister diseases caused by same thing