Histones (from calf thymus or from human placenta), if renatured in the presence of EDTA, caused a severe inhibition of in vitro methylation of double-stranded DNA (from Micrococcus luteus) by human placenta DNA methyltransferase. The absence of EDTA during the histone renaturation procedure abolished - at least in the 'physiological' range of the histones/DNA ratio - the inhibition. The H-1 component was responsible for this inhibition, no effect being exerted by the other histones. H-1 preparations were more effective if renatured in the presence of EDTA - 90% inhibition being reached at a 0.3:1 (w/w) H-1/DNA ratio. It seems likely that the requirement for the presence of EDTA during the renaturation process is correlated to its ability to induce a fairly stable ordered conformation of the histones, although this effect could also be shown with the 'inactive' H-2a, H-2b and H-3 components, and was instead less evident with histone H-1. The restriction to histone H-1 of the ability to inhibit enzymic DNA methylation may account for the lower methylation levels present in the internucleosomal DNA of mammalian chromatin.

Histones and DNA methylation in mammalian chromatin. Differential inhibition by histone H1

ALLEGRA, Paola;
1991-01-01

Abstract

Histones (from calf thymus or from human placenta), if renatured in the presence of EDTA, caused a severe inhibition of in vitro methylation of double-stranded DNA (from Micrococcus luteus) by human placenta DNA methyltransferase. The absence of EDTA during the histone renaturation procedure abolished - at least in the 'physiological' range of the histones/DNA ratio - the inhibition. The H-1 component was responsible for this inhibition, no effect being exerted by the other histones. H-1 preparations were more effective if renatured in the presence of EDTA - 90% inhibition being reached at a 0.3:1 (w/w) H-1/DNA ratio. It seems likely that the requirement for the presence of EDTA during the renaturation process is correlated to its ability to induce a fairly stable ordered conformation of the histones, although this effect could also be shown with the 'inactive' H-2a, H-2b and H-3 components, and was instead less evident with histone H-1. The restriction to histone H-1 of the ability to inhibit enzymic DNA methylation may account for the lower methylation levels present in the internucleosomal DNA of mammalian chromatin.
1991
1090
38
42
Paola Caiafa;Anna Reale;Paola Allegra;Matilde Rispoli;Maria D'Erme;Roberto Strom
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2318/112038
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