Nucleosome Cores and Histone H1 in the Binding of GAL4 Derivatives and the Reactivation of Transcription from Nucleosome Templates In Vitro

Abstract

The coupling of in vitro transcription and nucleosome assembly systems has allowed biochemical investigations into the role of nucleosomes in the transcription regulation of class II promoters. Previous studies demonstrated that the magnitude of transcription stimulation by activating factors could be enhanced at low template concentrations in nuclear extracts where nonspecific DNA-binding proteins repress basal transcription (Abmayr et al. 1985, 1988). Transcription was more dependent on the activator under repressive conditions than under nonrepressive conditions (i.e., at high DNA concentrations). These effects were recapitulated by a reconstituted nucleosome assembly system where repression of basal transcription and the resultant enhanced effect of transcription activators were dependent on the addition of either purified total histones (Workman et al. 1988) or core histones alone (Workman et al. 1991a). Thus, chromosomal structural proteins (histones) were shown to contribute to the regulation of transcription in vitro.