Figure 3.

Alignment-based gap filling by the pol λ DL mutant. Internally labeled (*) substrates bearing two 3′-overhangs (A) or one 3′- and one 5′-overhang (B) were incubated for 6 h in HeLa nuclear extracts that had been immunodepleted with either antibodies to pol λ (+), or preimmune antibodies (−), and supplemented with wild-type pol λ, pol λ /pol β chimera, pol λ DL or pol µ, as indicated. Samples were deproteinized, and DNA was cut with BstXI and AvaI and analyzed on denaturing gels. Schemes at top show mechanisms of formation of the major 43- and 42-base products. The 24- and 23-base products are formed by gap filling and ligation as shown in (A), except between the left-hand ends of two plasmid molecules.