RecQ Helicases: Conserved Guardians of Genomic Integrity.

The RecQ family of DNA helicases is highly conserved throughout -evolution, and is important for the maintenance of genome stability. In humans, five RecQ family members have been identified: BLM, WRN, RECQ4, RECQ1 and RECQ5. Defects in three of these give rise to Bloom's syndrome (BLM), Werner's syndrome (WRN) and Rothmund-Thomson/RAPADILINO/Baller-Gerold (RECQ4) syndromes. These syndromes are characterised by cancer predisposition and/or premature ageing. In this review, we focus on the roles of BLM and its S. cerevisiae homologue, Sgs1, in genome maintenance. BLM/Sgs1 has been shown to play a critical role in homologous recombination at multiple steps, including end-resection, displacement loop formation, branch migration and double Holliday junction dissolution. In addition, recent evidence has revealed a role for BLM/Sgs1 in the stabilisation and repair of replication forks damaged during a perturbed S-phase. Finally BLM also plays a role in the suppression and/or resolution of ultra-fine anaphase DNA bridges that form between sister-chromatids during mitosis.