TRANSCRIPTIONAL PROPERTIES OF OLIGONUCLEOSOMAL TEMPLATES CONTAINING ACETYLATED (H3-CENTER-DOT-H4)(2) TETRAMERS

Direct chemical acetylation of an oligonucleosomal template for bacter iophage T7 RNA polymerase is accompanied by a substantial increase in its capability to support RNA synthesis. The template was assembled fr om a plasmid, containing a promoter and a terminator for T7 RNA polyme rase, plus one (H3 . H4)(2) tetramer and two H2A . H2B dimers for each 200 base pairs of DNA. Under the employed conditions, acetylation mod ifies in a preferential way the lysine residues located in the amino-t erminal 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 report ed transcriptional stimulation upon acetylation of H2A . H2B dimers [P uerta et al. (1995) Biochem. Biophys. Res. Commun. 210, 409], the tran scriptional repression brought about by core histone octamers seems to require that the amino-terminal domains of both (H3 . H4)(2) tetramer s and H2A . H2B dimers are not acetylated. (C) 1995 academic Press, In c.