Hyperacetylation and differential deacetylation of histories H4 and H3 define two distinct classes of acetylated SV40 chromosomes early in infection

SV40 chromosomes undergoing encapsidation late in infection and SV40 chromatin in virions are hyperacetylated on histories H4 and H3. However, the fate of the SV40 chromosomes containing hyperacetylated histories in a subsequent round of infection has not been determined. In order to determine if SV40 chromosomes undergo changes in the extent of historic acetylation during early infection, we have analyzed SV40 chromosomes isolated 30 min and 3 h postinfection by quantitative ChIP assays, depletion ChIP assays, competitive ChIP assays, and ChIP assays combined with restriction endonuclease sensitivity using antibodies to hyperacetylated histories H4 and H3. We have shown that at 30 min postinfection, the hyperacetylated histories are associated with two distinct classes of SV40 chromosomes. One form is hyperacetylated specifically on histone H4 while a second form is hyperacetylated on both H4 and H3. Both forms of chromosomes appear to contain a nucleosome-free promoter region. Over the course of the next few hours of infection, the class of SV40 chromosomes hyperacetylated on only H4 is reduced or completely eliminated through deacetylation. (C) 2004 Elsevier Inc. All rights reserved.