Werner syndrome protein and the MRE11 complex are involved in a common pathway of replication fork recovery

Werner syndrome (WS) is an autosomal recessive disease that predisposes individuals to a wide range of cancers. The gene mutated in WS, WRN, encodes a member of the RecQ family of DNA helicases. The precise DNA metabolic processes in which WRN participates remain to be elucidated. However, it has been proposed that WRN might play an important role in the maintenance of genetic stability during DNA replication, possibly cooperating with other proteins. Here, we show that, following DNA replication arrest, WRN associates and colocalizes with the MRE11 complex at PCNA sites. We also provide evidence that both WRN/MRE11 complex association and proper WRN relocalization after HU treatment require a functional MRE11 complex. We demonstrate that mutations altering the functionality of WRN or that of the MRE11 complex result in chromosomal breakage during DNA replication and enhanced cell death following replication arrest. Finally, we show that the DNA breakage in replicating cells and apoptosis observed in WS are not enhanced by concomitant knock down of MRE11 by RNAi, indicating that WRN and MRE11 complex act in a common pathway. These results suggest a functional relationship between WRN and the MRE11 complex in response to replication fork arrest, disclosing a common action of WRN and the MRE11 complex in the pathway(s) preserving genome stability during DNA replication.