Lecture 10 Epigenetics and Cancer Flashcards Preview

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Flashcards in Lecture 10 Epigenetics and Cancer Deck (64)
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1

What are the two ways that regulating chromatin structure can be used to regulate gene expression

Controlling the accessibility to target genes of the transcription machinery and controlling the biochemical activity of the transcriptional machinery itself

2

How do epigenetic modifications differ from genetic modifications

Epigenetic modifications cause stable alterations to the chromatin structure but unlike genetic alterations these are reversible and do not involve changing the nucleotide sequence of DNA

3

What are the three broad categories of epigenetic modifications

Histone modifications (acetylation and methylation) DNA methylation and non-coding RNAs

4

What was Conrad Waddington’s contribution to the field of epigenetics

Conrad Waddington suggested that different cell fates during development are the end results of distinct journeys through an epigenetic landscape

5

In order for a haematopoietic stem cell to produce differentiated leukocytes and erythrocytes what phenomena need to occur

It needs to repress its ability to self-renew activate of program of lineage commitment and execute a program of terminal differentiation

6

What structures are referred to as the building blocks of chromatin

Nucleosomes

7

What is the effect of covalent modification of nucleosomes

Nucleosomes can be covalently modified which act as structural changes to the chromatin that effect gene transcription

8

What is significant about the tails of core histones

Nucleosome core histones have N-terminal lysine rich tails which project radially from the core. These can be reversibly covalently modified

9

Which residues are commonly acetylated by histone acetyltransferases

Lysine residues

10

Histone methyltransferases mono di or trimethylate which amino acids within the histone tails

Lysine and arginine

11

Acetylation and methylation of core histone tails can occur simultaneously T or F

F – methylation and acetylation are mutually exclusive and are competing modifications

12

Production of methylation marks prevents acetylation T or F

T

13

Histone acetyltransferases can modify many different lysine residues T or F

T

14

Histone methyltransferases can modify many different lysine or arginine residues T or F

F – histone methyltransferase exhibit exquisite site specificities

15

How many different enzymes methylate lysine 4 residues

6 different enzymes

16

How many different enzymes methylate lysine 9 residues

5 different enzymes

17

Which residues are methylated by CARM1

Arginine 17

18

Enhancer of zeste is one enzyme that methylates a lysine residue. What position in the polypeptide chain does it act

EZH2 methylates lysine 27

19

What is the role of EZH2 in development

EZH2 is a gene required to repress Hox gene expression in a specific anterior-posterior fashion

20

Histone methyltransferases act as regulators of gene transcription and are uniquely site specific T or F

T

21

Histone acetylases are uniquely site specific T or F

F – they acetylate a number of different lysine residues

22

What is meant by histone code writers

Histone methyltransferases are histone code writers they act as an additional code on top of the genetic code i.e. epigenetic to

23

What are the names of the enzymes that reverse histone acetylation and methylation respectively

Histone deacetylase and histone demethylase

24

Reversibility of the acetylation and methylation of histones accounts for what attribute of epigenetic changes

Means that they can be removed – aren’t permanent

25

Lysine acetylation is an indication of what

Transcriptionally active genes

26

Methylation can denote transcriptionally active or inactive genes depending on the loci of the residue. Determine whether methylation of lysine 4 9 27 and arginine 17 denote transcriptional activation or repression

Arginine 17 and Lysine 4 – transcriptionally active. Lysine 9 and 27 – transcriptionally inactive

27

How does methylation and acetylation of histone influence transcription

Acetylation and methylation marks in general create binding sites for transcription factors

28

Specifically what is the effect of histone acetylation on gene transcription

Acetylation of histones creates binding sites for transcriptional activation factors that contain a bromodomain. Histone Acetylation is associated primarily with transcriptionally active promoter sequences.

29

Will genes that are more transcriptionally active show higher or lower levels of acetylation

Higher

30

Methylation of core histones creates binding sites for transcriptional repressors that contain what kind of domain

Bromodomain