Recombinant XPG protein stimulates HPR. (A) A partially purified HeLa nuclear activity stimulates HPR by AG08802 extracts. Repair of substrate C-(CTG)25 was performed as described in the Figure 2 legend by mixing 75 μg of AG08802 nuclear extracts with 5 μl of individual HeLa fractions (HL Fr.) partially purified on a phosphocellulous P11 column . (B) Western analysis of the HPR-stimulating P11 fractions with an antibody against XPG. (C) Coomassie staining of an SDS polyacrylamide gel showing purified recombinant XPG protein. (D) HPR assays on substrates V-(CTG)25 and C-(CTG)25 by AG08802 nuclear extracts in the presence or absence of purified XPG protein, as indicated. Repair products are highlighted by red rectangles.