The gel image showing EXO1 exonuclease activity on a 3′ labelled DNA substrate. Representative gel of three independent biological experiments showing that nuclease activities on a 3′-radioactive labelled 42-mer dsDNA (GK142/GK143) (star denotes 3′-radiolabelling site), by incubation with recombinant purified EXO1. In lane 1, a radioactive labelled marker was used to indicate 12 bp (GK192). In lanes 2–4, dsDNA substrate, 3′ labelled was used. In lane 2, no EXO1 enzyme was added. In lanes 3 and 4, 2 and 4 pmol EXO1 was added, respectively, and the oligo was degraded for 30 min at 30°C.