DNAaseI-hypersensitive minichromosomes of SV40 possess an elastic torsional strain in DNA

Previously, we have shown that DNA in a small fraction (2–5%) of SV40 minichromosomes was torsionally strained and could be relaxed by treating minichromosomes with topoisomerase I. This fraction was enriched with endogoneous RNA polymerase II (Luchnik et al 1982, EMBO J., 1, 1353). Here we show tha...

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Published in:	Nucleic acids research Vol. 13; no. 4; pp. 1135 - 1149
Main Authors:	Luchnik, Andrey N., Bakayev, Valerii V., Yugai, Anatolii A., Zbarsky, Ilyia B., Georgiev, Georgii P.
Format:	Journal Article
Language:	English
Published:	England Oxford University Press 25-02-1985
Subjects:	Animals Cells, Cultured Cercopithecus aethiops Chromatin - physiology Chromatin - ultrastructure Deoxyribonuclease I DNA, Superhelical - genetics DNA, Viral - genetics Gene Expression Regulation Nucleic Acid Conformation Simian virus 40 - genetics
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Summary:	Previously, we have shown that DNA in a small fraction (2–5%) of SV40 minichromosomes was torsionally strained and could be relaxed by treating minichromosomes with topoisomerase I. This fraction was enriched with endogoneous RNA polymerase II (Luchnik et al 1982, EMBO J., 1, 1353). Here we show that one and the same fraction of SV4O 1 minichromosomes is hypersensitive to DNAase I and is relaxable by topoisomerase I. Moreover, this fraction completely loses its hypersensitivity to 1 DNAase I upon relaxation. The possibility that this fraction of minichromosomes can be represented by naked DNA is ruled out by the results of studying the kinetics of minichromosome digestion by DNAase I in comparison to digestion of pure SV40 DNA and by measuring the buoyant density of SV40 chromatin in equilibrium CaCl gradient. Our data obtained with SV4O minichromosomes may be relevant to the mechanism responsible for DNAase I hypersensitivity in the loops or domains of cellular chromatin.
Bibliography:	ArticleID:13.4.1135 istex:5AD270323633AE6B64979C996F68D333F94FA915 ark:/67375/HXZ-ZSKKX5CT-1 To whom reprint requests should be sent
ISSN:	0305-1048 1362-4962
DOI:	10.1093/nar/13.4.1135