Chemically induced gene expression. Manipulation of the transforming ability of simian virus 40 minichromatin by specific chemical hyperacetylation of histones H3 and H4.

We have developed a non-enzymatic acetylating procedure, closely resembling the situation in vivo, utilizing acetyl adenylate, an acetylating agent in vivo, that mimics the enzymatic hyperacetylation of specific histone species. Analysis of the acetylated species of calf thymus histones produced from reaction with soluble chromatin yielded the same species generated in vivo and observed during active gene transcription. Four species of histone H4 and three of histone H3 occur with no alteration in histones H2A or H2B. This procedure has been utilized to hyperacetylate simian virus 40 (SV40) minichromatin in vitro in order to study the effect of acetylated compared to non-acetylated minichromatin in cellular transformation of cultured Balb/3T3 cells. Transformed cell foci appeared only in the cultures infected with hyperacetylated SV40 minichromatin. To select for cellular transformation, foci were transferred to agar-lined culture flasks and grown in the suspension of 1% methylcellulose. The selected cells were plated on slides and analyzed for the presence of T-antigen by indirect immunofluorescence. The hyperacetylated-minichromatin-infected cells exhibited T-antigen-specific fluorescence, while non-acetylated-minichromatin-treated cells and normal cells showed no specific fluorescence. These results suggest a major role for histone hyperacetylation in the mechanism of SV40 viral transformation.