Linker histone binding to superhelical DNA: Electrophoretic and filter binding studies

It has been known for years that linker histones bind preferentially to sup ercoiled DNA. This preference has been demonstrated by a number of differen t techniques including deoxyribonucleoprotein electrophoresis, sedimentatio n, and filter binding under non-competitive conditions. In an attempt to fu rther study this issue, we used one- and two-dimensional electrophoretic ge ls and filter binding under competitive conditions, with all DNA forms of i nterest being simultaneously present in the incubation mixture. Comparison between results obtained by the two methods showed that whereas the prefere nce for superhelical molecules was clearly seen in the electrophoretic gels , the filter binding assay failed to reveal this preference. These results reveal limitations to the filter binding technique, which must be borne in mind in studies involving superhelical DNA molecules. (C) Societe francaise de biochimie et biologie moleculaire / Elsevier, Paris.