Figure 2.

CSB modulates SNM1A exonuclease activity. Single-stranded or double-stranded 3′-end labeled 61-mer (A) or 21-mer (B) oligonucleotides were incubated with SNM1A (+; fixed concentration of 0.8 nM), and increasing concentrations of CSB where indicated (0.8–50 nM), for 30 min at 37°C. Reactions were resolved on a denaturing gel, and images were captured during phosphorimager analysis (shown is a representative gel from three independent experiments). Note that the non-labeled strand of the double-stranded substrate is blocked at its 5′-end with a biotin moiety (B) to prevent competing digestion of this strand.