Histone acetylation in chicken erythrocytes. Estimation of the percentage of sites actively modified.

Within the N-terminal regions of the DNA-bound histone, 26 lysine residues per nucleosome may be acetylated and deacetylated. In the present paper the percentage of these residues actively acetylated and deacetylated in chicken erythrocytes was measured. This percentage is estimated as 3.7% in chicken immature, and 2.1% in chicken mature, erythrocytes. In metabolically active, dividing, cells one would predict that, after a few generations, each site would at some point in time be modified. We conclude that, in the relatively inactive immature chicken erythrocyte, no more than 1-2% of the genome is composed of dynamically acetylated and deacetylated histone, this percentage decreasing with cell maturity. The active histone acetylation and deacetylation may be confined to transcriptionally active or potentially active erythrocyte domains.