Abstract
Direct chemical acetylation of an oligonucleosomal template for bacteriophage T7 RNA polymerase is accompanied by a substantial increase in its capability to support RNA synthesis. The template was assembled from a plasmid, containing a promoter and a terminator for T7 RNA polymerase, plus one (H3·H4) 2 tetramer and two H2A·H2B dimers for each 200 base pairs of DNA. Under the employed conditions, acetylation modifies in a preferential way the lysine residues located in the amino-terminal domains of core histones. When the template is assembled with acetylated tetramers and untreated dimers, its efficiency in promoting RNA synthesis is also largely increased. Since a previous work reported transcriptional stimulation upon acetylation of H2A·H2B dimers [Puerta et al. (1995) Biochem. Biophys. Res. Commun. 210, 409], the transcriptional repression brought about by core histone octamers seems to require that the amino-terminal domains of both (H3·H4) 2 tetramers and H2A·H2B dimers are not acetylated.
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