Figure 3.

Abortive ligation by LIG1. (A) DNA denaturing gels comparing ligation of the 3′-DSB substrate by LIG1 and LIG3β at physiological Mg²⁺ (1 mM free Mg²⁺). (B) Fraction abortive intermediate and ligated product generated as a function of time by LIG1. Fraction species includes the reaction shown in A (left panel) and replicate reactions, all containing 100 nM 3′-DSB. (C) Greater than 70% of all adenylyl transfer events catalyzed by LIG1 generate adenylylated DNA intermediates, but abortive ligation by LIG3β was not detected (ND) (e.g. A, right panel). Equation 5 was used to calculate fraction abortive ligation from data obtained in reactions containing 50, 100 and 200 nM 3′-DSB (Supplementary Figure S8). Data in (B) are the average of three independent experiments, and data in (C) are the average of nine independent experiments (mean ± S.D.).