[Two types of DNA-pairing enzymatic activities detected in rat spermatocyte nuclei: partial purification and characteristics].

Two types of different activity that can promote homologous pairing and strand transfer between suitable DNA substrates have been partially purified from nuclear extracts of rat testes and characterized. Two activities are separated by chromatography on a ssDNA-cellulose column. One activity promotes strand transfer between single-strand circular phage and duplex fragment DNA (346 or 943 bp). The reaction does not require ATP and Mg2+. The other catalyzes only homologous pairing between duplex circular phage and single-strand fragment DNA (346 b). The activity does not need ATP, but requires Mg2+.