Homologous recombination catalyzed by mammalian cell extracts in vitro

An assay was developed to detect recombination events taking place in an in vitro reaction. Extracts of cultured mouse preB lymphocytes were found to catalyze homologous recombination between substrate DNA molecules but not site-specific recombination between cloned mouse immunoglobulin D and J genes. Addition of deoxyribonucleoside triphosphates increased the frequency of homologous recombination. This recombination activity was not observed in two differentiated lymphocyte cell lines.