Figure 4.

Potent inhibition of WRN and BLM helicase activities on an M13 partial duplex DNA substrate with a 4 bp A-T tract by the minor groove binder netropsin. WRN protein (96 nM) or BLM protein (19 nM) was incubated with the M13mp18: A-T[4] partial duplex DNA substrate in the presence of the indicated concentrations of netropsin under the standard helicase reaction conditions described in Materials and Methods. Helicase activity (% control activity) is expressed as a function of netropsin concentration. Closed circles, WRN; open circles, BLM. In control reactions, WRN or BLM helicase catalyzed unwinding of ∼50% of the partial duplex substrate. All data points are the average of at least three independent determinations.