Figure 2.

Exo- and endonuclease activities of wild-type (Wt) and mutant Exo1 proteins. (A) An aliquot of 1 pmol double-stranded (D.S.) blunt end DNA substrate was incubated with 0.01, 0.1 and 0.5 ng of the indicated protein and the nuclease reactions were analyzed on a polyacrylamide denaturing gel (see Materials and Methods). The positions of the substrate and mononucleotide (1 nt) are shown. The far left lane indicates the no protein control. (B) Endonuclease activities of wild-type (Wt) and mutant Hex1-N2 proteins were measured using a 5′-flap DNA substrate. The position of the flap junction incision product (10 nt) is shown. The substrates used in these assays and the specific activities of these proteins are given in Table 1.