Rec Q helicases


Group of 3’-5’ helicases required for genome stability. May also help to repair damaged/stalled replication forks.

(see also recQ4 included with sld2)



Helicases in this grouping


SpRqh1; hus2:rad12

BLM (hu/Xl))= FFA-1(Xl)  = mus309 (Dm)





Molecular weight


Biochemical properties



Can unwind and anneal DNA (1)



•Helicase 3’-5’, can also unwind odd structures eg tetrahelical structures

•3-5 Exonuclease (2)

• characterization replication fork regression (3)




 •Helicase 3’-5’, can also unwind odd structures eg tetrahelical structures and disrupt recombination intermediates.

•Strand annealing and exchange activity (4) likes to bind particularly to G4 DNA in long molecules (5)

• can regress stalled forks and dissolve Holliday junctions

•disrupts rad51 ssDNA filaments and stimulate repair synthesis (6)



•Helicase domain – note that these are all likely to be monomeric helicases (7)

•Walker A box ATPase

•RQC domain

•HRDC domain

•Exonuclease domain  (WRN, FFA-1)




• nls (8)


Sc (Sgs1)

•DNA topo III (9)

•topoII (10)


Sp (Rqh1)

•DNA topo III (11)

•Synthetically lethal pola (12)




•Pcna (13)

•Pol d (14) aids in passing hairpins in vitro (15) 50kDa subunit (16)

•Ku 70/80 (17) stimulates exo activity (18)

•Sumo /ubc9 (19)

•Fen 1 (20) (21)  

•Pot1 stimulates to unwind telomeric structures (22)

•P53 inhibits helicase activity (23)

•DNApk (24) inhibits ws activity.

•Blm (25)

•Rad52 (26)

• whip (27)

• multiple translesion polymerases (28)

• MSH2/6, MSH2/3 and MLH1/PMS2 (29)




•Pot1 stimulates to unwind telomeric structures (22)

•Caf150 (30) colocalise at sites replication, increased amounts on damage (blm inhibits caf mediated assembly).

•Fen1 (21)

•topoII (31)

•rad51 (32)

•p53 (33)

•wrn (25)

•scDNA2 (34)

•topoIII (35) and BLAP75 in complex to process Holliday junctions (36)

•fanc proteins (37)

•mlh1 (mismatch repair) (38)

• topoIII alpha (27)

• ATM (27)




•PCNA (39)



•Sumo (19)



Cellular location and expression


•Sgs1/Top3 may work in alternative pathway to Mus81/Mms4 for preventing formation of ‘toxic’ recombination intermediates formed by DNA replication (40)




• found in cytoplasm and nucleus (8)



•associates with dna replication factories in s and stays near the sites of stalled replication forks caused by uv damage (39)



Other comments

ReqQ mutants show increased homologous recombination

Hickson Nature Rev Cancer 3:169 (03) which recQ



•sgs 1 stabilises DNA polymerases at stalled replication forks (41)



• hus2/rqh1/rad12 (42)

•possible role on chromosome segregation (43)

•Cut phenotype in the presence hu (44) needed in recovery from stop/ stops recombination? see sgs




•Involved in hr but not nhej in xenopus extracts (45)

•Needed to load rpa at origins (not ssDNA dependent) in  xenopus extracts, but can deplete and replication ok and rpa still loads so redundant (46)


•Werners is a premature aging syndrome, roles in cell senescence and damage response (eg (47)

•Loss causes telomere loss (48) (45) (49)

•Accumulates at ds but nt ss breaks (50)

•Ws patients can’t do p53 mediated apoptosis. (51)

•Some role for acetylation for localisation on uv (52)

• accumulates in nucleolus (53)

• in vitro can carry out reaction equivalent to regression of a stalled replication fork (54)




•Localises to pml and needs p53 for this (51) (55)

•Cleaved caspase 3 (31)

•Delayed replication in blm cells (56)

•After hu treatment coalesces with p53 and rad51 at replication forks (57)

•needed to properly relocalise rad50/mre/nbs1 complex at sites replication arrest (58)

• in vitro can carry out reaction equivalent to regression of a stalled replication fork (59) (54) •blm,wrn and xpb and xpd can rescue some phenotypes of blm cells so partial redundancy

• role in sister chromatid disjunction (60)

• needed for efficient fork restart (61)

role with mus81 in recovering from replicative stress Other (62)


Deplete in xenopus extracts only minor effects on repair (63)


Ds break repair in flies (64)



• can promote strand exchange on a synthetic template resembling a stalled replication fork (39) (65)

•Knockout in chicken (66)

• phenotype in Dm (67)

• loss in mammals increases cancer susceptibility ( through HR /rad51?) (68)


Random recq helicases

•recQ1 – involved in processing of holliday junctions (69)

•recq helicase suggested to have a role in post transcriptional gene silencing in neurospora (70)


Revised by


Last edited

13 April 08



1.    Muzzolini,L., Beuron,F., Patwardhan,A., Popuri,V., Cui,S., Niccolini,B., Rappas,M., Freemont,P.S. and Vindigni,A. (2007) Different quaternary structures of human RECQ1 are associated with its dual enzymatic activity. PLoS Biol 5, e20.

2.    Kamath-Loeb,A.S., Shen,J.C., Loeb,L.A. and Fry,M. (1998) Werner syndrome protein. II. Characterization of the integral 3' --> 5' DNA exonuclease. J Biol Chem 273, 34145-34150.

3.    Machwe,A., Xiao,L., Lloyd,R.G., Bolt,E. and Orren,D.K. (2007) Replication fork regression in vitro by the Werner syndrome protein (WRN): holliday junction formation, the effect of leading arm structure and a potential role for WRN exonuclease activity. Nucleic Acids Res 35, 5729-5747.

4.    Bartos,J.D., Wang,W., Pike,J.E. and Bambara,R.A. (2006) Mechanisms by which Bloom protein can disrupt recombination intermediates of Okazaki fragment maturation. J Biol Chem 281, 32227-32239.

5.    Huber,M.D., Lee,D.C. and Maizels,N. (2002) G4 DNA unwinding by BLM and Sgs1p: substrate specificity and substrate-specific inhibition. Nucleic Acids Res 30, 3954-3961.

6.    Bugreev,D.V., Yu,X., Egelman,E.H. and Mazin,A.V. (2007) Novel pro- and anti-recombination activities of the Bloom's syndrome helicase. Genes Dev 21, 3085-3094.

7.    Sharma,S., Doherty,K.M. and Brosh,R.M.J. (2006) Mechanisms of RecQ helicases in pathways of DNA metabolism and maintenance of genomic stability. Biochem J 398, 319-337.

8.    Burks,L.M., Yin,J. and Plon,S.E. (2007) Nuclear import and retention domains in the amino terminus of RECQL4. Gene 391, 26-38.

9.    Gangloff,S., McDonald,J.P., Bendixen,C., Arthur,L. and Rothstein,R. (1994) The yeast type I topoisomerase Top3 interacts with Sgs1, a DNA helicase homolog: a potential eukaryotic reverse gyrase. Mol Cell Biol 14, 8391-8398.

10.  Watt,P.M., Louis,E.J., Borts,R.H. and Hickson,I.D. (1995) Sgs1: a eukaryotic homolog of E. coli RecQ that interacts with topoisomerase II in vivo and is required for faithful chromosome segregation. Cell 81, 253-260.

11.  Ahmad,F. and Stewart,E. (2005) The N-terminal region of the Schizosaccharomyces pombe RecQ helicase, Rqh1p, physically interacts with Topoisomerase III and is required for Rqh1p function. Mol Genet Genomics 273, 102-114.

12.  Bhaumik,D. and Wang,T.S. (1998) Mutational effect of fission yeast polalpha on cell cycle events. Mol Biol Cell 9, 2107-2123.

13.  Lebel,M., Spillare,E.A., Harris,C.C. and Leder,P. (1999) The Werner syndrome gene product co-purifies with the DNA replication complex and interacts with PCNA and topoisomerase I. J Biol Chem 274, 37795-37799.

14.  Kamath-Loeb,A.S., Johansson,E., Burgers,P.M. and Loeb,L.A. (2000) Functional interaction between the Werner Syndrome protein and DNA polymerase delta. Proc Natl Acad Sci U S A 97, 4603-4608.

15.  Kamath-Loeb,A.S., Loeb,L.A., Johansson,E., Burgers,P.M. and Fry,M. (2001) Interactions between the Werner syndrome helicase and DNA polymerase delta specifically facilitate copying of tetraplex and hairpin structures of the d(CGG)n trinucleotide repeat sequence. J Biol Chem 276, 16439-16446.

16.  Szekely,A.M., Chen,Y.H., Zhang,C., Oshima,J. and Weissman,S.M. (2000) Werner protein recruits DNA polymerase delta to the nucleolus. Proc Natl Acad Sci U S A 97, 11365-11370.

17.  Cooper,M.P., Machwe,A., Orren,D.K., Brosh,R.M., Ramsden,D. and Bohr,V.A. (2000) Ku complex interacts with and stimulates the Werner protein. Genes Dev 14, 907-912.

18.  Orren,D.K., Machwe,A., Karmakar,P., Piotrowski,J., Cooper,M.P. and Bohr,V.A. (2001) A functional interaction of Ku with Werner exonuclease facilitates digestion of damaged DNA. Nucleic Acids Res 29, 1926-1934.

19.  Kawabe,Y., Seki,M., Seki,T., Wang,W.S., Imamura,O., Furuichi,Y., Saitoh,H. and Enomoto,T. (2000) Covalent modification of the Werner's syndrome gene product with the ubiquitin-related protein, SUMO-1. J Biol Chem 275, 20963-20966.

20.  Sharma,S., Otterlei,M., Sommers,J.A., Driscoll,H.C., Dianov,G.L., Kao,H.I., Bambara,R.A. and Brosh,R.M.J. (2004) WRN helicase and FEN-1 form a complex upon replication arrest and together process branchmigrating DNA structures associated with the replication fork. Mol Biol Cell 15, 734-750.

21.  Sharma,S., Sommers,J.A., Gary,R.K., Friedrich-Heineken,E., Hubscher,U. and Brosh,R.M.J. (2005) The interaction site of Flap Endonuclease-1 with WRN helicase suggests a coordination of WRN and PCNA. Nucleic Acids Res 33, 6769-6781.

22.  Opresko,P.L., Mason,P.A., Podell,E.R., Lei,M., Hickson,I.D., Cech,T.R. and Bohr,V.A. (2005) POT1 stimulates RecQ helicases WRN and BLM to unwind telomeric DNA substrates. J Biol Chem 280, 32069-32080.

23.  Brosh,R.M.J., Karmakar,P., Sommers,J.A., Yang,Q., Wang,X.W., Spillare,E.A., Harris,C.C. and Bohr,V.A. (2001) p53 Modulates the exonuclease activity of Werner syndrome protein. J Biol Chem 276, 35093-35102.

24.  Yannone,S.M., Roy,S., Chan,D.W., Murphy,M.B., Huang,S., Campisi,J. and Chen,D.J. (2001) Werner syndrome protein is regulated and phosphorylated by DNA-dependent protein kinase. J Biol Chem 276, 38242-38248.

25.  von Kobbe,C., Karmakar,P., Dawut,L., Opresko,P., Zeng,X., Brosh,R.M.J., Hickson,I.D. and Bohr,V.A. (2002) Colocalization, physical, and functional interaction between Werner and Bloom syndrome proteins. J Biol Chem 277, 22035-22044.

26.  Baynton,K., Otterlei,M., Bjoras,M., von Kobbe,C., Bohr,V.A. and Seeberg,E. (2003) WRN interacts physically and functionally with the recombination mediator protein RAD52. J Biol Chem 278, 36476-36486.

27.  Hickson,I.D. (2003) RecQ helicases: caretakers of the genome. Nat Rev Cancer 3, 169-178.

28.  Kamath-Loeb,A.S., Lan,L., Nakajima,S., Yasui,A. and Loeb,L.A. (2007) Werner syndrome protein interacts functionally with translesion DNA polymerases. Proc Natl Acad Sci U S A 104, 10394-10399.

29.  Saydam,N., Kanagaraj,R., Dietschy,T., Garcia,P.L., Pena-Diaz,J., Shevelev,I., Stagljar,I. and Janscak,P. (2007) Physical and functional interactions between Werner syndrome helicase and mismatch-repair initiation factors. Nucleic Acids Res 35, 5706-5716.

30.  Jiao,R., Bachrati,C.Z., Pedrazzi,G., Kuster,P., Petkovic,M., Li,J.L., Egli,D., Hickson,I.D. and Stagljar,I. (2004) Physical and functional interaction between the Bloom's syndrome gene product and the largest subunit of chromatin assembly factor 1. Mol Cell Biol 24, 4710-4719.

31.  Freire,R., d'Adda Di Fagagna,F., Wu,L., Pedrazzi,G., Stagljar,I., Hickson,I.D. and Jackson,S.P. (2001) Cleavage of the Bloom's syndrome gene product during apoptosis by caspase-3 results in an impaired interaction with topoisomerase IIIalpha. Nucleic Acids Res 29, 3172-3180.

32.  Wu,L., Davies,S.L., Levitt,N.C. and Hickson,I.D. (2001) Potential role for the BLM helicase in recombinational repair via a conserved interaction with RAD51. J Biol Chem 276, 19375-19381.

33.  Garkavtsev,I.V., Kley,N., Grigorian,I.A. and Gudkov,A.V. (2001) The Bloom syndrome protein interacts and cooperates with p53 in regulation of transcription and cell growth control. Oncogene 20, 8276-8280.

34.  Imamura,O. and Campbell,J.L. (2003) The human Bloom syndrome gene suppresses the DNA replication and repair defects of yeast dna2 mutants. Proc Natl Acad Sci U S A 100, 8193-8198.

35.  Wu,L. and Hickson,I.D. (2003) The Bloom's syndrome helicase suppresses crossing over during homologous recombination. Nature 426, 870-874.

36.  Bussen,W., Raynard,S., Busygina,V., Singh,A.K. and Sung,P. (2007) Holliday junction processing activity of the BLM-Topo IIIalpha-BLAP75 complex. J Biol Chem282, 31484-31492.

37.  Meetei,A.R., Sechi,S., Wallisch,M., Yang,D., Young,M.K., Joenje,H., Hoatlin,M.E. and Wang,W. (2003) A multiprotein nuclear complex connects Fanconi anemia and Bloom syndrome. Mol Cell Biol 23, 3417-3426.

38.  Pedrazzi,G., Perrera,C., Blaser,H., Kuster,P., Marra,G., Davies,S.L., Ryu,G.H., Freire,R., Hickson,I.D., Jiricny,J. and Stagljar,I. (2001) Direct association of Bloom's syndrome gene product with the human mismatch repair protein MLH1. Nucleic Acids Res 29, 4378-4386.

39.  Kanagaraj,R., Saydam,N., Garcia,P.L., Zheng,L. and Janscak,P. (2006) Human RECQ5beta helicase promotes strand exchange on synthetic DNA structures resembling a stalled replication fork. Nucleic Acids Res 34, 5217-5231.

40.  Fabre,F., Chan,A., Heyer,W.D. and Gangloff,S. (2002) Alternate pathways involving Sgs1/Top3, Mus81/ Mms4, and Srs2 prevent formation of toxic recombination intermediates from single-stranded gaps created by DNA replication. Proc Natl Acad Sci U S A 99, 16887-16892.

41.  Cobb,J.A., Schleker,T., Rojas,V., Bjergbaek,L., Tercero,J.A. and Gasser,S.M. (2005) Replisome instability, fork collapse, and gross chromosomal rearrangements arise synergistically from Mec1 kinase and RecQ helicase mutations. Genes Dev 19, 3055-3069.

42.  Davey,S., Han,C.S., Ramer,S.A., Klassen,J.C., Jacobson,A., Eisenberger,A., Hopkins,K.M., Lieberman,H.B. and Freyer,G.A. (1998) Fission yeast rad12+ regulates cell cycle checkpoint control and is homologous to the Bloom's syndrome disease gene. Mol Cell Biol 18, 2721-2728.

43.  Win,T.Z., Mankouri,H.W., Hickson,I.D. and Wang,S.W. (2005) A role for the fission yeast Rqh1 helicase in chromosome segregation. J Cell Sci 118, 5777-5784.

44.  Stewart,E., Chapman,C.R., Al-Khodairy,F., Carr,A.M. and Enoch,T. (1997) rqh1+, a fission yeast gene related to the Bloom's and Werner's syndrome genes, is required for reversible S phase arrest. EMBO J 16, 2682-2692.

45.  Laud,P.R., Multani,A.S., Bailey,S.M., Wu,L., Ma,J., Kingsley,C., Lebel,M., Pathak,S., DePinho,R.A. and Chang,S. (2005) Elevated telomere-telomere recombination in WRN-deficient, telomere dysfunctional cells promotes escape from senescence and engagement of the ALT pathway. Genes Dev 19, 2560-2570.

46.  Chen,C.Y., Graham,J. and Yan,H. (2001) Evidence for a replication function of FFA-1, the Xenopus orthologue of Werner syndrome protein. J Cell Biol152, 985-996.

47.  Szekely,A.M., Bleichert,F., Numann,A., Van Komen,S., Manasanch,E., Ben Nasr,A., Canaan,A. and Weissman,S.M. (2005) Werner protein protects nonproliferating cells from oxidative DNA damage. Mol Cell Biol 25, 10492-10506.

48.  Crabbe,L., Verdun,R.E., Haggblom,C.I. and Karlseder,J. (2004) Defective telomere lagging strand synthesis in cells lacking WRN helicase activity. Science 306, 1951-1953.

49.  Lee,J.Y., Kozak,M., Martin,J.D., Pennock,E. and Johnson,F.B. (2007) Evidence that a RecQ helicase slows senescence by resolving recombining telomeres. PLoS Biol5, e160.

50.  Lan,L., Nakajima,S., Komatsu,K., Nussenzweig,A., Shimamoto,A., Oshima,J. and Yasui,A. (2005) Accumulation of Werner protein at DNA double-strand breaks in human cells. J Cell Sci 118, 4153-4162.

51.  Wang,X.W., Tseng,A., Ellis,N.A., Spillare,E.A., Linke,S.P., Robles,A.I., Seker,H., Yang,Q., Hu,P., Beresten,S., Bemmels,N.A., Garfield,S. and Harris,C.C. (2001) Functional interaction of p53 and BLM DNA helicase in apoptosis. J Biol Chem276, 32948-32955.

52.  Blander,G., Zalle,N., Daniely,Y., Taplick,J., Gray,M.D. and Oren,M. (2002) DNA damage-induced translocation of the Werner helicase is regulated by acetylation. J Biol Chem 277, 50934-50940.

53.  Carmo-Fonseca,M., Mendes-Soares,L. and Campos,I. (2000) To be or not to be in the nucleolus. Nat Cell Biol 2, E107-12.

54.  Machwe,A., Xiao,L., Groden,J. and Orren,D.K. (2006) The Werner and Bloom syndrome proteins catalyze regression of a model replication fork. Biochemistry 45, 13939-13946.

55.  Bischof,O., Kim,S.H., Irving,J., Beresten,S., Ellis,N.A. and Campisi,J. (2001) Regulation and localization of the Bloom syndrome protein in response to DNA damage. J Cell Biol 153, 367-380.

56.  Rassool,F.V., North,P.S., Mufti,G.J. and Hickson,I.D. (2003) Constitutive DNA damage is linked to DNA replication abnormalities in Bloom's syndrome cells. Oncogene22, 8749-8757.

57.  Sengupta,S., Linke,S.P., Pedeux,R., Yang,Q., Farnsworth,J., Garfield,S.H., Valerie,K., Shay,J.W., Ellis,N.A., Wasylyk,B. and Harris,C.C. (2003) BLM helicase-dependent transport of p53 to sites of stalled DNA replication forks modulates homologous recombination. EMBO J 22, 1210-1222.

58.  Franchitto,A. and Pichierri,P. (2002) Bloom's syndrome protein is required for correct relocalization of RAD50/MRE11/NBS1 complex after replication fork arrest. J Cell Biol 157, 19-30.

59.  Ralf,C., Hickson,I.D. and Wu,L. (2006) The Bloom's syndrome helicase can promote the regression of a model replication fork. J Biol Chem 281, 22839-22846.

60.  Chan,K.L., North,P.S. and Hickson,I.D. (2007) BLM is required for faithful chromosome segregation and its localization defines a class of ultrafine anaphase bridges. EMBO J 26, 3397-3409.

61.  Davies,S.L., North,P.S. and Hickson,I.D. (2007) Role for BLM in replication-fork restart and suppression of origin firing after replicative stress. Nat Struct Mol Biol 14, 677-679.

62.  Shimura,T., Torres,M.J., Martin,M.M., Rao,V.A., Pommier,Y., Katsura,M., Miyagawa,K. and Aladjem,M.I. (2008) Bloom's syndrome helicase and Mus81 are required to induce transient double-strand DNA breaks in response to DNA replication stress. J Mol Biol 375, 1152-1164.

63.  Liao,S., Graham,J. and Yan,H. (2000) The function of Xenopus Bloom's syndrome protein homolog (xBLM) in DNA replication. Genes Dev 14, 2570-2575.

64.  Adams,M.D., McVey,M. and Sekelsky,J.J. (2003) Drosophila BLM in double-strand break repair by synthesis-dependent strand annealing. Science 299, 265-267.

65.  Garcia,P.L., Liu,Y., Jiricny,J., West,S.C. and Janscak,P. (2004) Human RECQ5beta, a protein with DNA helicase and strand-annealing activities in a single polypeptide. EMBO J 23, 2882-2891.

66.  Wang,W., Seki,M., Narita,Y., Nakagawa,T., Yoshimura,A., Otsuki,M., Kawabe,Y., Tada,S., Yagi,H., Ishii,Y. and Enomoto,T. (2003) Functional relation among RecQ family helicases RecQL1, RecQL5, and BLM in cell growth and sister chromatid exchange formation. Mol Cell Biol 23, 3527-3535.

67.  Nakayama,M., Maruyama,S., Kanda,H., Ohkita,N., Nakano,K., Ito,F. and Kawasaki,K. (2006) Relationships of Drosophila melanogaster RECQ5/QE to cell-cycle progression and DNA damage. FEBS Lett 580, 6938-6942.

68.  Hu,Y., Raynard,S., Sehorn,M.G., Lu,X., Bussen,W., Zheng,L., Stark,J.M., Barnes,E.L., Chi,P., Janscak,P., Jasin,M., Vogel,H., Sung,P. and Luo,G. (2007) RECQL5/Recql5 helicase regulates homologous recombination and suppresses tumor formation via disruption of Rad51 presynaptic filaments. Genes Dev 21, 3073-3084.

69.  LeRoy,G., Carroll,R., Kyin,S., Seki,M. and Cole,M.D. (2005) Identification of RecQL1 as a Holliday junction processing enzyme in human cell lines. Nucleic Acids Res33, 6251-6257.

70.  Cogoni,C. and Macino,G. (1999) Posttranscriptional gene silencing in Neurospora by a RecQ DNA helicase. Science 286, 2342-2344.