ANALYSIS OF THE MAMMALIAN RECOMBINATION PROTEIN COMPLEX RC-1

Based on a novel cell-free assay for DNA recombination, we previously reported the purification and initial characterization of RC-1, a prot ein complex catalyzing the recombinational repair of deletions and gap s. RC-1 was isolated from calf thymus nuclear extracts and shown to co purify with several enzymatic activities, among them a DNA polymerase. Here, additional evidence is reported identifying the polymerase as D NA polymerase E. Furthermore, a novel DNA structure-de pendent endonuc lease associated with RC-1 was observed, which recognizes and cleaves branched DNA substrates at specific sites. Implications of this endonu clease activity for the recombination reaction are discussed.