Partial purification of an activity from human cells that promotes homologous pairing and the formation of heteroduplex DNA in the presence of ATP.

An activity that can promote homologous pairing and strand transfer between suitable DNA substrates has been partially purified from human skin fibroblasts and from HeLa cells. The strand transfer reaction was investigated with DNA substrates consisting of single-stranded circular and duplex linear phage DNA. It requires ATP, and under optimal conditions yields heteroduplex molecules containing one strand from each parental DNA substrate. The reactions appears to be of the same general nature as those mediated by RecA proteins of Escherichia coli and the Rec1 protein of Ustilago maydis.