RecQ enzymes are broadly conserved Superfamily-2 (SF-2) DNA helicases that play critical roles in DNA metabolism. RecQ proteins use the energy of ATP hydrolysis to drive DNA unwinding; however, the mechanisms by which RecQ links ATPase activity to DNA-binding/unwinding are unknown. In many Superfamily-1 (SF-1) DNA helicases, helicase sequence motif III links these activities by binding both sin...

Maintenance of genome integrity is the major biological role of RecQ-family helicases via their participation in homologous recombination (HR)-mediated DNA repair processes. RecQ helicases exert their functions by using the free energy of ATP hydrolysis for mechanical movement along DNA tracks (translocation). In addition to the importance of translocation per se in recombination processes, kno...

RecQ helicases are evolutionarily conserved enzymes required for the maintenance of genome stability. Mutations in three of the five known human RecQ helicase genes cause distinct clinical disorders that are characterized by genome instability and cancer predisposition. Recent studies have begun to reveal the cellular roles of RecQ helicases and how these enzymes may prevent tumorigenesis at th...

RecQ4 is a member of the RecQ helicase family, an evolutionarily conserved class of enzymes, dedicated to preserving genomic integrity by operating in telomere maintenance, DNA repair and replication. While reduced RecQ4 activity is associated with cancer predisposition and premature aging, RecQ4 upregulation is related to carcinogenesis and metastasis. Within the RecQ family, RecQ4 assumes an ...

Since the cloning of the first human RECQ gene, RECQ1, more than 15 years ago, RECQ helicases have been a major focus in cancer research. Recent studies of human RECQ protein complexes are providing insight into their roles in various DNA metabolic pathways that protect the integrity of our genome.

We demonstrate that RecQ helicase from Escherichia coli is a catalytic helicase whose activity depends on the concentration of ATP, free magnesium ion, and single-stranded DNA-binding (SSB) protein. Helicase activity is cooperative in ATP concentration, with an apparent S(0.5) value for ATP of 200 microm and a Hill coefficient of 3.3 +/- 0.3. Therefore, RecQ helicase utilizes multiple, interact...

Together, RecQ helicase and topoisomerase III (Topo III) of Escherichia coli comprise a potent DNA strand passage activity that can catenate covalently closed DNA (Harmon, F. G., DiGate, R. J., and Kowalczykowski, S. C. (1999) Mol. Cell 3, 611-620). Here we directly assessed the structure of the catenated DNA species formed by RecQ helicase and Topo III using atomic force microscopy. The images...

Human cells express five DNA helicases that are paralogs of Escherichia coli RecQ and which constitute the family of human RecQ helicases. Disease-causing mutations in three of these five human DNA helicases, BLM, WRN, and RECQL4, cause rare severe human genetic diseases with distinct clinical phenotypes characterized by developmental defects, skin abnormalities, genomic instability, and cancer...

DNA helicases are motor proteins that unwind double-stranded DNA (dsDNA) to reveal single-stranded DNA (ssDNA) needed for many biological processes. The RecQ helicase is involved in repairing damage caused by DNA breaks and stalled replication forks via homologous recombination. Here, the helicase activity of RecQ was visualized on single molecules of DNA using a fluorescent sensor that directl...

The processing of various DNA structures by RecQ helicases is crucial for genome maintenance in both bacteria and eukaryotes. RecQ helicases perform active destabilization of DNA duplexes, based on tight coupling of their ATPase activity to moderately processive translocation along DNA strands. Here, we determined the ATPase kinetic mechanism of E. coli RecQ helicase to reveal how mechanoenzyma...