Figure 5.
DNA replication decreases the uracil content. (a) Model of the effect of DNA replication on uracil content, with the presumption that AID functions within the first 24 h of stimulation. The U:G mispair would then be replicated so that one daughter cell receives a U:A pair and the other receives a C:G pair, thus diminishing the uracil content by half. When replication is blocked by aphidicolin, uracil residues accumulate. (b) Quantitative PCR analysis of the amplification of Sμ in DNA from Ung−/− B cells (presented as in Fig. 3b). *P = 0.04 and **P = 0.000038 (two-tailed t-test). Data are from four independent experiments (error bars, s.e.m.). (c) Southern blot analysis (top) of DNA from Ung−/− B cells treated with APE1 with or without UNG and separated by electrophoresis through alkaline agarose gels. Below, quantification of uracil content in treated samples, standardized to Dhfr intensity and presented relative to that of untreated samples. *P = 0.02 and **P = 0.0001 (two-tailed t-test). Data are from at least two independent experiments (error bars, s.e.m.).