Saravanabhavan Thangavel 1 , Matteo Berti 1 , Maryna Levikova 2 , Cosimo Pinto 2 , Shivasankari Gomathinayagam 1 , Marko Vujanovic 2 , Ralph Zellweger 2 , Hayley Moore 3 , Eu Han Lee 4 , Eric A. Hendrickson 4 , Petr Cejka 2 , Sheila Stewart 3 , Massimo Lopes 2 , Alessandro Vindigni , 1
2 March 2015
Following prolonged genotoxic stress, DNA2 and WRN functionally interact to degrade reversed replication forks and promote replication restart, thereby preventing aberrant processing of unresolved replication intermediates
Accurate processing of stalled or damaged DNA replication forks is paramount to genomic integrity and recent work points to replication fork reversal and restart as a central mechanism to ensuring high-fidelity DNA replication. Here, we identify a novel DNA2- and WRN-dependent mechanism of reversed replication fork processing and restart after prolonged genotoxic stress. The human DNA2 nuclease and WRN ATPase activities functionally interact to degrade reversed replication forks with a 5′-to-3′ polarity and promote replication restart, thus preventing aberrant processing of unresolved replication intermediates. Unexpectedly, EXO1, MRE11, and CtIP are not involved in the same mechanism of reversed fork processing, whereas human RECQ1 limits DNA2 activity by preventing extensive nascent strand degradation. RAD51 depletion antagonizes this mechanism, presumably by preventing reversed fork formation. These studies define a new mechanism for maintaining genome integrity tightly controlled by specific nucleolytic activities and central homologous recombination factors.