Aguilera 9603905 An enzyme which is thought to be involved in the lymphocyte-specific process of immunoglobulin isotype-class switch recombination has been identified and partially purified. The enzyme preferentially cleaves tgggg and tgagc switch repeat motifs commonly found at switch recombination breakpoints. The enzyme activity has been purified to near homogeneity from nuclear extracts of murine b lymphocytes and bovine splenocytes. Preliminary biochemical characterization with the purified enzyme, now called endo-sr, support the initial assumption that the enzyme is novel. The biochemical characterization will be continued in the search for data to validate the hypothesis that this enzyme is a putative switch endonuclease activity. To that end, work will be initiated to clone the gene based upon the information gained by determining the peptide composition of the purified enzyme. Further characterization of the various factors, including the involved enzyme(s), implicated in somatic DNA rearrangements in lymphocytes should lead to a better understanding of not only the ig switch recombination process but also the underlying mechanisms of somatic DNA recombination in mammalian cells.
