Multiple RPAs make WRN syndrome protein a superhelicase
Abstract RPA is known to stimulate the helicase activity of Werner syndrome protein (WRN) but the exact stimulation mechanism is not understood. We use single molecule FRET and magnetic tweezers to investigate the helicase activity of WRN and its stimulation by RPA. We show that WRN alone is a weak helicase which repetitively unwind just a few tens of base pairs, but that binding of multiple RPAs to the enzyme converts WRN into a superhelicase that unidirectionally unwinds double stranded DNA more than 1 kb. Our study provides a good case in which the activity and biological functions of the enzyme may be fundamentally altered by the binding of cofactors.
Nucleic acids research