Sammendrag
Base excision repair (BER) is initiated by a DNA glycosylase and is c ompleted by alternative routes, one of which requires proliferating c ell nuclear antigen (PCNA) and other proteins also involved in DNA re plication. We report that the major nuclear uracil-DNA glycosylase (U NG2) increases in S phase, during which it co-localizes with incorpor ated BrdUrd in replication foci. Uracil is rapidly removed from repli catively incorporated dUMP residues in isolated nuclei. Neutralizing antibodies to UNG2 inhibit this removal, indicating that UNG2 is the major uracil-DNA glycosylase responsible. PCNA and replication protei n A (RPA) co-localize with UNG2 in replication foci, and a direct mol ecular interaction of UNG2 with PCNA (one binding site) and RPA (two binding sites) was demonstrated using two-hybrid assays, a peptide SP OT assay and enzyme-linked immunosorbent assays. These results demons trate rapid post-replicative removal of incorporated uracil by UNG2 a nd indicate the formation of a BER complex that contains UNG2, RPA an d PCNA close to the replication fork.
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