FIG. 4.

Modulation of polyomavirus DNA replication in murine cell extracts by human replication factors. In vitro DNA replication in the presence of equal amounts of purified recombinant BKV, mPyV, and SV40 TAg (shaded bars) using mouse FM3A cell extracts is shown. Bars 1 to 4 show DNA synthesis in the presence of mouse cell extracts and either mPyV TAg/P-P-P, BKV TAg/B-B-B, or SV40 TAg/pOriSV40. Incorporation of dNMPs into P-P-P in the absence of TAg served as a negative control. DNA synthesis with mouse cell extract and additional human DNA Pol α-primase (2 units of hPol α-primase) (66) is depicted in bars 5 to 7 (mPyV TAg/P-P-P, BKV TAg/B-B-B, and SV40 TAg/pOriSV40, respectively). The DNA synthesis of mouse cell extracts with an additional 0.5 μg of hRPA using mPyV TAg/P-P-P and BKV TAg/B-B-B is presented in bars 8 and 9, respectively, whereas the influence of human topoisomerase I (hTopo I, 120 ng) on the DNA synthesis in the presence of mouse cell extracts with mPyV TAg/P-P-P and BKV TAg/B-B-B is shown in bars 10 and 11, respectively. All assays were carried out in triplicate, and the results presented are the averages from two independent experiments.