Figure 4. Mechanistically distinct regulators of alt DNA pols are required to facilitate unperturbed DNA replication.
(A) W.B. analysis revealing PCNA, ubi-PCNA and p21 levels in U2OS cells transfected with the indicated siRNAs. (B) USP1 mRNA levels were examined by quantitative RT-PCR. (C) Model depicting the different mechanisms of PCNA regulation by p21 and USP1. (D) IdU track length was measured in 85 fibers/sample in three independent experiments. (E) Origin firing frequency. 150 fibers/sample were analysed in three independent experiments. (F) Quantification of cells with more than five 53BP1 foci. 200 U2OS cells/sample were analysed in three independent experiments. (G) MN accumulation. 300 binucleated cells/sample were analyzed in three independent experiments. Data on the effect of USP1 downregulation on the modulation of nascent DNA elongation (Figure 4D) and accumulation of cells with 53BP1 foci (Figure 4F) and micronuclei (Figure 4G) was reproduced from Jones et al, EMBO.