Figure 1.

Esa1p is a histone acetyltransferase. (A) No enzyme (bars −) and bacterial-expressed Gcn5p, Hat1p, Esa1p, or vector only (bars vec.) were incubated without substrate (bars 1), with chicken erythrocyte core histones (bars 2), or with BSA (bars 3), and [³H]acetate incorporation was measured by a filter binding assay. (B) Specificity for core histone acetylation was assessed by separating reaction products on a 15% SDS/PAGE gel, staining with Coomassie blue, and fluorography. (Upper) Fluorogram. (Lower) The corresponding Coomassie-stained gel. Although the level of H2A acetylation by Esa1p is relatively low, it is reproducible. (C) Individual chicken histones were purified by reverse-phase HPLC, and equivalent amounts of each histone were incubated with Esa1p and processed for fluorography as above. H4, H2A, and H3 are well acetylated by Esa1p when presented individually.