Histone H1 represses transcription from minichromosomes assembled in vitro.

Abstract

We have previously shown that transcription from a Xenopus 5S rRNA gene assembled into chromatin in vitro can be repressed in the absence of histone H1 at high nucleosome densities (one nucleosome per 160 base pairs of DNA) (A. Shimamura, D. Tremethick, and A. Worcel, Mol. Cell. Biol. 8:4257-4269, 1988). We report here that transcriptional repression may also be achieved at lower nucleosome densities (one nucleosome per 215 base pairs of DNA) when histone H1 is present. Removal of histone H1 from the minichromosomes with Biorex under conditions in which no nucleosome disruption was observed led to transcriptional activation. Transcriptional repression could be restored by adding histone H1 back to the H1-depleted minichromosomes. The levels of histone H1 that repressed the H1-depleted minichromosomes failed to repress transcription from free DNA templates present in trans. The assembly of transcription complexes onto the H1-depleted minichromosomes protected the 5S RNA gene from inactivation by histone H1.

Mechanism of transcriptional antirepression by GAL4-VP16.

“…H1 has an important role in the structure of chromatin and is required for the compaction of chromatin into the 30-nm filament (Finch and Klug 1976;Renz et al 1977;Thoma et al 1979;Butler and Thomas 1980). In addition, a number of studies have suggested that HI is involved in transcriptional repression and is depleted from the promoter regions of transcriptionally active genes (Schlissel and Brown 1984;Nacheva et al 1989;Shimamura et al 1989;Wolffe 1989;Kamakaka and Thomas 1990;Postnikov et al 1991;Bresnick et al 1992). Thus, the finding that sequence-specific factors are able to counteract Hi-mediated transcriptional repression (Croston et al 1991a;Layboum and Kadonaga 1991) was consistent with previous results that have implicated H1 as a repressor of basal transcription.…”

Dissociation of Protamine‐DNA Complexes by Xenopus Nucleoplasmin and Minichromosome Assembly in vitro

“…The distribution centre of the latter appears displaced by 1 or 2 bands. Considering that the formation of each nucleosome introduces a linking number change of one in the covalently closed circular DNA (Germond et al, 1975), the shift observed between the two topoisomer ladders reveals a relative difference of 1 or 2 in the number of nucleosomes in minichromosomes assembled with protein $1 in respect to the 18 regularly spaced nucleosonies reported for a fully loaded minichromosome assembled in the absence of exogenous protein (Rodriguez-Campos et al, 1989). These results are consistent with those of the MN digestion analysis as well as with the notion that the interaction of protein 41 with DNA somehow hinders the process of minichromosome assembly.…”

“…5 , (Wray et al, 1981) to enhance protein detection. The slowly migrating inaterial in the minichromosome lanes (MCs) corresponds to some contaminating proteins of the ,5150 extract known to cosediment with assembled minichromosomes and which resolve on the high-molecular-mass range of the SDS-gels (Shimamura et al, 1988(Shimamura et al, , 1989Zucker and Woreel, 1990). The protein composition found correlates further to the preceding results concerning the MN digestion and DNA topology analyses as well as those of the hydrodynamic behaviour of the minichromosome formed over the DNA-41 complex.…”

Oocyte-specific linker histone H1foo is an epigenomic modulator that decondenses chromatin and impairs pluripotency

“…18,19 The chromatin architecture determines the gene activity associated with epigenetic changes. 14,15 The chromatin structure is open at H1foo target genes; thus, H1foo is likely a biphasic epigenetic regulator.…”