Histone acetylation: a switch between repressive and permissive chromatin. Second in review series on chromatin dynamics

Abstract

The organization of eukaryotic chromatin has a major impact on all nuclear processes involving DNA substrates. Gene expression is affected by the positioning of individual nucleosomes relative to regulatory sequence elements, by the folding of the nucleosomal fiber into higher-order structures and by the compartmentalization of functional domains within the nucleus. Because site-specific acetylation of nucleosomal histones influences all three aspects of chromatin organization, it is central to the switch between permissive and repressive chromatin structure. The targeting of enzymes that modulate the histone acetylation status of chromatin, in synergy with the effects mediated by other chromatin remodeling factors, is central to gene regulation.

Fig. 1. The histone acetylation switch. Targeted HAT and HDAC activities negotiate the acetylation status of chromatin. Acetylation establishes a structure that permits ATP-dependent chromatin remodeling factors to open promoters. Deacetylation, frequently followed by histone methylation, may form a solid base for highly repressive structures, such as heterochromatin. Acetylated histone tails are shown as yellow circles. Methylations are indicated as gray rectangles. HAT, histone acetyltransferase; HDAC, histone deacetylase; HMT, histone methyltransferase; HP1, heterochromatin protein 1.

Anton Eberharter & Peter B. Becker