DIFFERENTIAL REPRESSION OF TRANSCRIPTION FACTOR-BINDING BY HISTONE H1IS REGULATED BY THE CORE HISTONE AMINO TERMINI

In order to investigate the interrelated roles of nucleosome cores and histone H1 in transcription repression, we have employed a purified s ystem to analyze the function of H1 in the repression of transcription factor binding to nucleosomes. H1 binding to nucleosome cores resulte d in the repression of USF binding to nucleosomes. By contrast, H1 onl y slightly inhibited the binding of GAL4-AH, indicating that H1 differ entially represses the binding of factors with different DNA-binding d omains. H1-mediated repression of factor binding was dependent on the core histone aminoterminal tails. Removal of these domains alleviated Hi-mediated repression and increased acetylation of these domains part ly alleviated repression by H1. H1 binding assays suggest a less stabl e interaction of histone H1 with the core particle in the absence of t he amino termini.