RecQ

RecQ is a family of DNA helicases named after the Escherichia coli RecQ protein. Members of this family are found across bacteria, archaea, and eukaryotes and play a central role in maintaining genome stability by participating in DNA replication, repair, and recombination.

Molecular features: RecQ helicases typically unwind duplex DNA using ATP hydrolysis in a 3' to 5' direction. They share a conserved N-terminal helicase domain containing the Walker A and B motifs and the Q motif, plus a C-terminal RecQ helicase–RNase-like domain (RQC) that often coordinates a zinc ion. In many eukaryotes, a C-terminal HRDC (helicase-and-RNaseD-like C-terminal) domain modulates DNA binding. The exact substrate range varies; some RecQ proteins preferentially unwind forked DNA, G-quadruplexes, or Holliday junctions, and they often promote branch migration or dissolution rather than simple unwinding.

Biological roles: In bacteria, RecQ participates in the RecF pathway for DNA repair and replication restart, processing DNA ends and stalled forks in coordination with SSB. In eukaryotes, the RecQ paralogs—BLM, WRN, RECQL1, RECQL4, and RECQ5—contribute to homologous recombination, replication fork maintenance, and telomere integrity. The yeast Sgs1 and human WRN/BLM proteins are especially known for processing Holliday junctions and preventing excessive recombination.

Clinical relevance: Germline mutations in BLM, WRN, and RECQL4 cause Bloom syndrome, Werner syndrome, and Rothmund–Thomson syndrome, respectively, with genome instability and cancer predisposition or premature aging. Altered RecQ function is also implicated in cancer susceptibility and therapy response.

Research context: RecQ helicases are widely studied as models of DNA repair and genome maintenance. Structural and biochemical studies illuminate their DNA substrate preferences and partner interactions with BRCA1/2, RAD51, FANCM, and others; their roles in G-quadruplex unwinding and fork processing are areas of active investigation.