DNA synthesis by pol δ in the presence of the PCNA proteins. (A) An autoradiogram of the products of pol δ-catalyzed DNA synthesis on a non-damaged DNA substrate in the presence of no PCNA, the wild-type PCNA protein, the C22Y mutant PCNA protein, and the C81R mutant PCNA protein. The position of the fully extended, runoff product is indicated with an arrow. (B) An autoradiogram of the products of pol δ-catalyzed DNA synthesis on an abasic site-containing DNA substrate in the presence of no PCNA, the wild-type PCNA protein, the C22Y mutant PCNA protein, and the C81R mutant PCNA protein. The position of the abasic site is indicated by an X, and the position of the fully extended, runoff product is indicated with an arrow.