DNA replication in nuclei isolated from bovine lymphocytes.

DNA replication was studied in nuclei isolated from phytohemagglutin-stimulated bovine lymphocytes. The mitogen treatment induced more than 60% of these cells to engage in DNA synthesis with a peak of synthetic activity occurring about 48 h after the addition of phytohemagglutinin. Throughout this response the ability of isolated nuclei and nuclear sonicates to synthesize DNA in vitro was proportional to the synthetic ability of the intact cells of origin. The subcellular systems appear to continue synthesis at replicative sites which were active in vivo. The rate of in vitro synthesis by both nuclei and nuclear sonicates was about two-thirds that of intact cells. The one cytoplasmic and two nuclear DNA polymerase activities separated from these cells were found to have properties similar to those of other eucaryotic cells.