Figure 1.
RPA-p34 phosphorylation in asynchronous normal and A-T cells exposed to 10 J/m2 UVC. Cell lysates (A and B) or nuclear extracts (C) were prepared from asynchronously growing cells at indicated times after 10 J/m2 UV radiation or mock exposure. The p34 subunit of RPA was detected by Western immunoblotting with monoclonal antibody 34A. Phosphorylation causes a slower migration on the gel; at least five different forms of the p34 subunit of RPA can be visualized. (A) RPA-p34 in LM217 cells; (B) RPA-p34 in AT5BIVA cells; (C) RPA-p34 in nuclear lysates of GM00637 (lanes 1 and 2), AT5BIVA (lanes 3 and 4), and AT3BISV (lanes 5 and 6) cells. Band 1 is unphosphorylated RPA-p34; bands 2 and 3 are cell cycle–dependent phosphorylated forms; and band 5 is the DNA damage–induced hyperphosphorylated form.