DNA secondary structure of the released strand stimulates WRN helicase action on forked duplexes without coordinate action of WRN exonuclease

► In this study, we investigated the effect of a DNA secondary structure on the two WRN activities. ► We found that a DNA secondary structure of the displaced strand during unwinding stimulates WRN helicase without coordinate action of WRN exonuclease. ► These results imply that WRN helicase and exonuclease activities can act independently.