Fig. 6. RPA foci assemble in MCM3-depleted extracts. (A) Western blot of Xenopus egg supernatants (S1, S2) and protein precipitates (P) resulting from a single (S1) or double (S2) immunodepletion with either control mouse IgG (mock) or an anti-MCM3 monoclonal antibody (Materials and Methods). (B) Sperm nuclei were incubated in mock () or MCM3-depleted extracts () for different times. DNA replication was followed by incorporation of [³²P]dCTP. (C,D) Sperm nuclei were incubated in mock- or MCM3-depleted extracts, in the presence of biotin dUTP, as described in Materials and Methods. Samples were treated with 0.3% Triton X-100 before formaldehyde fixation, for the analysis of chromatin-bound proteins by immunofluorescence with antibodies specific for the indicated proteins.