SAR-dependent mobilization of histone H1 by HMG-I/Y in vitro: HMG-I/Y is enriched in H1-depleted chromatin.
An experimental assay was developed to search for proteins capable of antagonizing histone H1-mediated general repression of transcription. T7 RNA polymerase templates containing an upstream scaffold-associated region (SAR) were highly selectively repressed by H1 relative to non-SAR control templates. This is due to the nucleation of H1 assembly into flanking DNA brought about by the numerous A-tracts (AT-rich sequences containing short homopolymeric runs of dA.dT base pairs) of the SAR. Partial, selective titration of these A-tracts by the high mobility group (HMG) protein HMG-I/Y led to the complete derepression of transcription from the SAR template by inducing the redistribution of H1 on to non-SAR templates. SARs are associated with many highly transcribed regulated genes where they may serve to facilitate the HMG-I/Y-mediated displacement of histone H1 in chromatin. Indeed, HMG-I/Y was found to be strongly enriched in the H1-depleted subfraction which can be isolated from chromatin.
Zhao
K
K
Department of Molecular Biology and Biochemistry, University of Geneva, Switzerland.
Käs
E
E
Gonzalez
E
E
Laemmli
U K
UK
D000818:Animals; D001483:Base Sequence; D002843:Chromatin / Q000378:metabolism*; D004247:DNA / Q000378:metabolism*; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism; D006609:High Mobility Group Proteins / Q000378:metabolism*; D006657:Histones / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008969:Molecular Sequence Data; D051381:Rats; D013698:Templates, Genetic; D014158:Transcription, Genetic; D014764:Viral Proteins
D002843:Chromatin; D006609:High Mobility Group Proteins; D006657:Histones; D014764:Viral Proteins; D004247:DNA; C062210:bacteriophage T7 RNA polymerase; D012321:DNA-Directed RNA Polymerases