Transcription Regulation

Housekeeping genes

Unique or differentiation specific genes

Chromatin

Chromosomes

Euchromatin

Heterochromatin

First DNA packing stage

Histones

Nucelosome

H2A - H2B - H3 - H4

H3-H4 Heterotetramer

H2A-H2B Dimer

H1

Beads on a string

Histone Core

Histone Tail

30 nm fiber

False

True (Nucleosome formation is preferential at certain DNA sequences)

Nuclesome Formation

Heterochromatin

Histone Acetylation

HATs (Histone Acetyltransferases)

HDACs (Histone Deacetylases)

Methylation of H3 Lysine 9

Methylation of H3 Lysine 4

Histone Methylation

Chromodomains

Histone code

Histone Phosphorylation

Histone Ubiquitination

Chromatin Remodeling Complexes

• ATPase domain (universal)
• Bromodomain (binds acetylated lysines)
• Chromodomain (binds methylated lysines)
• SANT-SLIDE (binds histone tails)

One Model: CRC creates a distortion around the histone octamer, which results in sliding of octamer to a new position on the DNA

Direct DNA modification

DNA methyltransferase

Methylated cytosines are more likely to undergo spontaneous deamination

5-M cytosine will deaminate into Tyrosine

DNA methylation

X-chromosome inactivation

In females, one X chromosomes is deactivated. An effect of this occurs in cats, where coloring is connected to the X chromosome. Depending on the X gene deactivated, causes different patches of colored fur.