Structure of the helicase core of Werner Helicase, a key target in microsatellite instability cancers

Loss of WRN, a DNA repair helicase, was identified as a strong vulnerability of microsatellite instable(MSI) cancers, making WRN a promising drug target. We show that ATP binding and hydrolysis are required for genome integrity and viability of MSI cancer cells. We report a 2.2 Å crystal structure of the WRN helicase core (517-1093), comprising the two helicase subdomains and winged helix domain but not the HRDC domain or nuclease domains. The structure highlights unusual features: First, an atypical mode of nucleotide binding that results in unusual relative positioning of the two helicase subdomains. Second, an additional β-hairpin in the second helicase subdomain and an unusual helical hairpin in the Zn2+ binding domain. Modelling of the WRN helicase in complex with DNA suggests roles for these features in the binding of alternative DNA structures. NMR analysis of shows a weak interaction between the HRDC domain and the helicase core, indicating a possible biological role for this association. Together, this study will facilitate the structure-based development of inhibitors against WRN helicase.