BLM (Bloom)

2005-05-01   Mounira Amor-Guéret 





4.4kb mRNA



1417 amino acids; ATP binding in amino acid 689-696; DEAH box in 795-798; two putative nuclear localization signals in the C-term in 1334-1349


accumulates to high levels in S phase of the cell cycle, persists in G2/M and sharply declines in G1. Hyperphoshorylated in mitosis


nuclear (PML nuclear bodies and nucleolus)


  • 3-5DNA helicase; probable role in DNA replication and double-strand break repair
  • Preferred substrates : G-quadruplex DNA, D-loops structures and X-junctions.
  • Recombinant protein promotes ATP-dependent branch migration of Hollyday junctions, effects, with topoisomerase III?, the resolution of a recombination intermediate containing a double Holliday junction with no flanking sequence exchanges, and possess a strand pairing activity.
  • Recombinant BLM possess a strand pairing activity.
  • Participates in a supercomplex of BRCA1 -associated proteins named BASC (BRCA1-Associated genome Surveillance Complex) containing ATM (defective in ataxia telangiectasia), NBS1 (defective in Nijmegen syndrome) and MRE11 (defective in ataxia-telangiectasia-like disorder), MLH1, MSH2 and MSH6, which are involved in human non-polyposis colorectal cancer, RAD50 and DNA replication factor C.
  • Participates in a complex named BRAFT (BLM, RPA, FA, Topoisomerase III) containing five of the Fanconia Anemia (FA) complementation group proteins (FANCA, FANCG, FANCC, FANCE and FANCF).
  • Interacts physically and/or functionally with p53, 53BP1, WRN, MLH1, RAD51, TRF2, ATR, the largest subunit of CAF-1, ligase IV, FEN1, Mus81, the monoubiquitinated FANCD2 isoform
  • Is Associated with telomeres and ribosomal DNA repeats.
  • Is phosphorylated in mitotic cells through the cdc2 pathway, and in response to DNA damaging agents or stalled replication forks.
  • Homology

    homologous to RecQ helicases, a subfamily of DExH box-containing helicases; in particular, similarity with the four known human members in the RecQ subfamily, human RecQL, human Wrn, the product of the Werner syndrome gene, and the human RecQL4, involved in the Rothmund-Thomson syndrome, and RecQL5 proteins



    five BLM mutations introducing amino acid substitutions and four BLM mutations introducing premature nonsense codons into the coding sequence have been described to date; one BLM mutation consisting in a 6 bp deletion accompanied by a 7 bp insertion at nucleic acid position 2281 is common in patients from Ashkenazi Jewish ancestry, leading to a truncated protein of 739 amino acids in length; two BLM mutations, 631delCAA and 1610insA were detected in japanese patients.

    Implicated in

    Entity name
    Bloom syndrome
    Bloom syndrome is a chromosome instability syndrome/cancer prone disease (at risk of numerous, early occurring cancers of various types)
    1/3 of patients are dead at mean age 24 yrs, and the mean age of the 2/3 remaining alive patients is 22 yrs
    chromatid/chromosome breaks; triradial and quadriradial figures, highly elevated spontaneous sister chromatid exchange rate


    Pubmed IDLast YearTitleAuthors
    119603802002Bloom's syndrome protein response to ultraviolet-C radiation and hydroxyurea-mediated DNA synthesis inhibition.Ababou M et al
    108621052000Identification of a novel BLM missense mutation (2706T>C) in a Moroccan patient with Bloom's syndrome.Barakat A et al
    156042582004A major role for mitotic CDC2 kinase inactivation in the establishment of the mitotic DNA damage checkpoint.Bayart E et al
    113094172001Regulation and localization of the Bloom syndrome protein in response to DNA damage.Bischof O et al
    117419242002Dephosphorylation and subcellular compartment change of the mitotic Bloom's syndrome DNA helicase in response to ionizing radiation.Dutertre S et al
    88752521996Molecular genetics of Bloom's syndrome.Ellis NA et al
    75859681995The Bloom's syndrome gene product is homologous to RecQ helicases.Ellis NA et al
    92857781997Characterization of a new BLM mutation associated with a topoisomerase II alpha defect in a patient with Bloom's syndrome.Foucault F et al
    117818422001The Bloom syndrome protein interacts and cooperates with p53 in regulation of transcription and cell growth control.Garkavtsev IV et al
    119711872002Increased error-prone non homologous DNA end-joining--a proposed mechanism of chromosomal instability in Bloom's syndrome.Gaymes TJ et al
    105255301999PML is critical for ND10 formation and recruits the PML-interacting protein daxx to this nuclear structure when modified by SUMO-1.Ishov AM et al
    151431662004Physical and functional interaction between the Bloom's syndrome gene product and the largest subunit of chromatin assembly factor 1.Jiao R et al
    152898972004Relatively common mutations of the Bloom syndrome gene in the Japanese population.Kaneko H et al
    93884801997BLM (the causative gene of Bloom syndrome) protein translocation into the nucleus by a nuclear localization signal.Kaneko H et al
    93881931997The Bloom's syndrome gene product is a 3'-5' DNA helicase.Karow JK et al
    108238972000The Bloom's syndrome gene product promotes branch migration of holliday junctions.Karow JK et al
    98782471998Cloning of two new human helicase genes of the RecQ family: biological significance of multiple species in higher eukaryotes.Kitao S et al
    120191522002The BLM helicase is necessary for normal DNA double-strand break repair.Langland G et al
    106786592000Rothmund-Thomson syndrome due to RECQ4 helicase mutations: report and clinical and molecular comparisons with Bloom syndrome and Werner syndrome.Lindor NM et al
    158455382005RecQ family members combine strand pairing and unwinding activities to catalyze strand exchange.Machwe A et al
    127244012003A multiprotein nuclear complex connects Fanconi anemia and Bloom syndrome.Meetei AR et al
    114330312001The Bloom's and Werner's syndrome proteins are DNA structure-specific helicases.Mohaghegh P et al
    145763162003Possible anti-recombinogenic role of Bloom's syndrome helicase in double-strand break processing.Onclercq-Delic R et al
    121813132002Telomere-binding protein TRF2 binds to and stimulates the Werner and Bloom syndrome helicases.Opresko PL et al
    116919252001Direct association of Bloom's syndrome gene product with the human mismatch repair protein MLH1.Pedrazzi G et al
    79619771994Cloning and characterization of RECQL, a potential human homologue of the Escherichia coli DNA helicase RecQ.Puranam KL et al
    145778412003Telomere and ribosomal DNA repeats are chromosomal targets of the bloom syndrome DNA helicase.Schawalder J et al
    75271361994Molecular cloning of cDNA encoding human DNA helicase Q1 which has homology to Escherichia coli Rec Q helicase and localization of the gene at chromosome 12p12.Seki M et al
    153649582004Functional interaction between BLM helicase and 53BP1 in a Chk1-mediated pathway during S-phase arrest.Sengupta S et al
    155095772004Genetic interactions between BLM and DNA ligase IV in human cells.So S et al
    124440982002The Bloom syndrome helicase BLM interacts with TRF2 in ALT cells and promotes telomeric DNA synthesis.Stavropoulos DJ et al
    97652921998The Bloom's syndrome helicase unwinds G4 DNA.Sun H et al
    155799052005Human Bloom protein stimulates flap endonuclease 1 activity by resolving DNA secondary structure.Wang W et al
    113997662001Functional interaction of p53 and BLM DNA helicase in apoptosis.Wang XW et al
    107831652000BASC, a super complex of BRCA1-associated proteins involved in the recognition and repair of aberrant DNA structures.Wang Y et al
    112785092001Potential role for the BLM helicase in recombinational repair via a conserved interaction with RAD51.Wu L et al
    120800662002The processing of Holliday junctions by BLM and WRN helicases is regulated by p53.Yang Q et al
    107795602000Nuclear structure in normal and Bloom syndrome cells.Yankiwski V et al
    86025091996Positional cloning of the Werner's syndrome gene.Yu CE et al
    158052432005BLM helicase facilitates Mus81 endonuclease activity in human cells.Zhang R et al
    110874182000Binding and melting of D-loops by the Bloom syndrome helicase.van Brabant AJ et al
    119191942002Colocalization, physical, and functional interaction between Werner and Bloom syndrome proteins.von Kobbe C et al

    Other Information

    Locus ID:

    NCBI: 641
    MIM: 604610
    HGNC: 1058
    Ensembl: ENSG00000197299


    dbSNP: 641
    ClinVar: 641
    TCGA: ENSG00000197299


    Gene IDTranscript IDUniprot

    Expression (GTEx)



    PathwaySourceExternal ID
    Homologous recombinationKEGGko03440
    Homologous recombinationKEGGhsa03440
    Fanconi anemia pathwayKEGGko03460
    Fanconi anemia pathwayKEGGhsa03460
    BRCA1-associated genome surveillance complex (BASC)KEGGhsa_M00295
    Bloom's syndrome complexKEGGhsa_M00414
    BRCA1-associated genome surveillance complex (BASC)KEGGM00295
    Bloom's syndrome complexKEGGM00414
    Metabolism of proteinsREACTOMER-HSA-392499
    Post-translational protein modificationREACTOMER-HSA-597592
    SUMO E3 ligases SUMOylate target proteinsREACTOMER-HSA-3108232
    SUMOylation of DNA damage response and repair proteinsREACTOMER-HSA-3108214
    Gene ExpressionREACTOMER-HSA-74160
    Generic Transcription PathwayREACTOMER-HSA-212436
    Transcriptional Regulation by TP53REACTOMER-HSA-3700989
    Cell CycleREACTOMER-HSA-1640170
    Cell Cycle CheckpointsREACTOMER-HSA-69620
    G2/M CheckpointsREACTOMER-HSA-69481
    G2/M DNA damage checkpointREACTOMER-HSA-69473
    Meiotic recombinationREACTOMER-HSA-912446
    DNA RepairREACTOMER-HSA-73894
    DNA Double-Strand Break RepairREACTOMER-HSA-5693532
    Homology Directed RepairREACTOMER-HSA-5693538
    HDR through Homologous Recombination (HR) or Single Strand Annealing (SSA)REACTOMER-HSA-5693567
    Processing of DNA double-strand break endsREACTOMER-HSA-5693607
    HDR through Homologous Recombination (HRR)REACTOMER-HSA-5685942
    Homologous DNA Pairing and Strand ExchangeREACTOMER-HSA-5693579
    Presynaptic phase of homologous DNA pairing and strand exchangeREACTOMER-HSA-5693616
    Resolution of D-Loop StructuresREACTOMER-HSA-5693537
    Resolution of D-loop Structures through Holliday Junction IntermediatesREACTOMER-HSA-5693568
    Resolution of D-loop Structures through Synthesis-Dependent Strand Annealing (SDSA)REACTOMER-HSA-5693554
    HDR through Single Strand Annealing (SSA)REACTOMER-HSA-5685938
    Regulation of TP53 ActivityREACTOMER-HSA-5633007
    Regulation of TP53 Activity through PhosphorylationREACTOMER-HSA-6804756

    Protein levels (Protein atlas)

    Not detected


    Pubmed IDYearTitleCitations
    146852452003The Bloom's syndrome helicase suppresses crossing over during homologous recombination.495
    213251342011BLM-DNA2-RPA-MRN and EXO1-BLM-RPA-MRN constitute two DNA end resection machineries for human DNA break repair.301
    175990642007BLM is required for faithful chromosome segregation and its localization defines a class of ultrafine anaphase bridges.164
    180038602007Novel pro- and anti-recombination activities of the Bloom's syndrome helicase.152
    189713432008Human exonuclease 1 and BLM helicase interact to resect DNA and initiate DNA repair.152
    165374862006BLAP75/RMI1 promotes the BLM-dependent dissolution of homologous recombination intermediates.151
    194659212009The FANC pathway and BLM collaborate during mitosis to prevent micro-nucleation and chromosome abnormalities.140
    121813132002Telomere-binding protein TRF2 binds to and stimulates the Werner and Bloom syndrome helicases.137
    165956952006A double Holliday junction dissolvasome comprising BLM, topoisomerase IIIalpha, and BLAP75.123
    167665182006The Bloom's syndrome helicase can promote the regression of a model replication fork.112


    Mounira Amor-Guéret

    BLM (Bloom)

    Atlas Genet Cytogenet Oncol Haematol. 2005-05-01

    Online version:

    Historical Card

    2000-09-01 BLM (Bloom) by  Mounira Amor-Guéret 

    1998-02-01 BLM (Bloom) by  Jean-Loup Huret 

    Genetics, Dept Medical Information, University of Poitiers, CHU Poitiers Hospital, F-86021 Poitiers, France