Unwinding of short fully hybridized strands. Time course for the unwinding of M2:M1 by WRN ( A ) or DHX9 ( B ), unwinding of R2:R1 by WRN ( C ) and DHX9 ( D ), and melting of M2:R1 by WRN ( E ) or DHX9 ( F ) 28 nM of WRN or of DHX9 and 1 nM of substrates were used for each experiment. Triangle represents heat-denatured DNA substrate control, NE no enzyme. The positions of the substrates and reaction products are indicated; double lines depict RNA containing strands. The asterisk represents the 5′-labeled nucleotide. Quantifications of duplex unwinding by WRN ( G ) and DHX9 ( H ) are also depicted. Error bars indicate SD as derived from three independent experiments.