Histone variants

Question 1

H3.3?

Answer 1

A variant of H3 with only 4aa difference. However, this 4aa difference is evolutionarily conserved. Present in both active genes and constitutive heterochromatin

Question 2

CenH3?

Answer 2

aka CENP-A. Present specifically in centrosomal chromatin.

Question 3

What are two H3 veriants

Answer 3

H3.3 and CenH3

Question 4

(gamma)H2AX

Answer 4

recruited at DSBs. gamma means phosphorylated

Question 5

When are new H2AX recruited to chromatin?

Answer 5

gamma-H2AX can be
added at any time during the cell cycle as DSB can happen at anytime not just S phase

Question 6

H2A.Z?

Answer 6

active promoters. H2A.Z wraps DNA more tightly, which will have
consequences on how gene transcription will proceed. In plants for example, its loading onto chromatin is somewhat
temperature-dependent.

Question 7

mH2A?

Answer 7

macroH2A. Only present in vertebrates. It has 200aa more than the regular H2A, and is
enriched on the inactive X chromosome. (m = mommy)

Question 8

H2A.B?

Answer 8

It is deposited at sites where
active transcription, splicing, etc are happening, but only in testis cells. (B = balls)