Characterization of a 3'-5' exonuclease associated with VDJP

VDJP (V(D)J RSS Dependent DNA Joining Protein) was cloned based on binding to the nonamer portion of the V(D)J recombinational signal sequence (RSS), and genetic analysis revealed that VDJP is encoded by the same gene as the large subunit of Replication Factor C (RF-C). Recombinant VDJP has a site directed DNA joining activity and is capable of forming a covalent bond between DNA fragments containing an RSS element near their ends and exhibits 3' to 5' exonuclease activity. In this report, we examine the biochemical properties of the VDJP exonuclease activity such as directionality of nuclease action (3' to 5' or 5' to 3'), single-strand substrate preference, cleavage products, dependence on cofactors and metal cations, and optimal reaction conditions. From this analysis, we conclude that VDJP has an intrinsic 3'-5' exonuclease activity that produces mononucleotide products.