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The chromatin‐associated protein H‐NS alters DNA topology in vitro.
Author(s) -
Tupper A.E.,
OwenHughes T.A.,
Ussery D.W.,
Santos D.S.,
Ferguson D.J.,
Sidebotham J.M.,
Hinton J.C.,
Higgins C.F.
Publication year - 1994
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1002/j.1460-2075.1994.tb06256.x
Subject(s) - library science , operations research , classics , sociology , management , history , computer science , mathematics , economics
H‐NS is one of the two most abundant proteins in the bacterial nucleoid and influences the expression of a number of genes. We have studied the interaction of H‐NS with DNA; purified H‐NS was demonstrated to constrain negative DNA supercoils in vitro. This provides support for the hypothesis that H‐NS influences transcription via changes in DNA topology, and is evidence of a structural role for H‐NS in bacterial chromatin. The effects of H‐NS on topology were only observed at sub‐saturating concentrations of the protein. In addition, a preferred binding site on DNA was identified by DNase I footprinting at sub‐saturating H‐NS concentrations. This site corresponded to a curved sequence element which we previously showed, by in vivo studies, to be a site at which H‐NS influences transcription of the proU operon. When present in saturating concentrations, H‐NS did not constrain supercoils and bound to DNA in a sequence‐independent fashion, covering all DNA molecules from end to end, suggesting that H‐NS may form distinct complexes with DNA at different H‐NS:DNA ratios. The data presented here provide direct support for the hypothesis that H‐NS acts at specific sites to influence DNA topology and, hence, transcription.