Fig. 1.

BLM stimulates resection of dsDNA by hExo1. Nuclease reactions were performed by using 3′ end-labeled EcoRI-linearized pUC19 as described in Materials and Methods. (A) Gel showing time courses. Lanes: 1–3, BLM; 4–6, hExo1b and BLM; 7–9, hExo1b; 10–12, BLM; 13–15, hExo1a and BLM; and 16–18, hExo1a. (B) Quantification of hExo1 activity. The percentage of intact dsDNA remaining, from experiments as shown in A, was determined relative to the 0-min time points (100%). Error bars indicate variation between multiple preparations and independent experiments and were determined by using GraphPad Prism version 4. (C) Gel showing stimulation of Exo1 (20 nM) as a function of BLM concentration (0, 20, 40, and 80 nM) after 5 min; lanes: 1, absence of proteins; and 2–5, increasing concentration of BLM. The positions of the intact substrate (2.7 kbp), resection products, and molecular size standards (kbp) are indicated.