Modification of Histones:

Histones are subject to a wide range of modifications of their amino acid tails:

o Methylation and acetylation of lysine residues

o Phosphorylation

o Attachment of ubiquitin

HOW DO THESE MODIFICATIONS CAUSE A CHANGE IN TRANSCRIPTION RATE?

Cis model

Acetylation of the amino acid chain can neutralise the positively charged amine group. This means that the negatively charged DNA is bound more loosely to the histone and so is more accessible for transcription

Trans model

The hypothesis that these modifications alter gene transcription is called the ‘histone code’

o The histone modifications serve to recruit other proteins which specifically recognise the alteration

o These proteins then alter chromatin structure to modify transcription

	Created by Ellie Quinn over 10 years ago

Note on Epigenetic Mechanisms, created by Ellie Quinn on 05/02/2014.

Epigenetic Mechanisms