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Symbol BLM contributors: mct/ - updated : 02-09-2018
HGNC name Bloom syndrome, RecQ helicase-like
HGNC id 1058
Corresponding disease
BLMS Bloom syndrome
Location 15q26.1      Physical location : 91.260.578 - 91.358.684
Synonym name
  • RECQ protein-like 3
  • DNA helicase, RecQ-like type 2
  • Synonym symbol(s) BS, RECQL3, RECQ2, RECQL2, MGC126616, MGC131618, MGC131620, RMI2, C16orf75, BLAP18, C16orf75
    TYPE functioning gene
    STRUCTURE 98.13 kb     22 Exon(s)
    10 Kb 5' upstream gene genomic sequence study
    MAPPING cloned Y linked Y status confirmed
    Map cen - D15S1131 - D15S996 - D15S1153 - D15S1159 - D15S1108 - BLM - D15S1132 - D15S1141 - D15S1130 - D15S1142 - D15S1129 - D15S1143 - D15S1144 - D15S1145 - D15S1146 - D15S1147 - D15S1148 - D15S1149 - D15S127 - D15S1150 - FURIN - FES - D15S1151 - D15S1152 - D15S158 - D15S1120 - D15S1139 - D15S1133 - qter
    TRANSCRIPTS type messenger
    identificationnb exonstypebpproduct
    ProteinkDaAAspecific expressionYearPubmed
    23 - 4665 - 1417 - -
    22 - 4528 158 1417 - 1995 7485150
    22 - 4721 - 1042 - -
    20 - 4162 - 1286 - -
       expressed in (based on citations)
    SystemOrgan level 1Organ level 2Organ level 3Organ level 4LevelPubmedSpeciesStageRna symbol
    blood / hematopoieticthymus    
    Digestiveintestinelarge intestinecolon highly
    Lymphoid/Immunelymph node   highly
     tonsils   highly
    Reproductivemale systemtestis   
    SystemTissueTissue level 1Tissue level 2LevelPubmedSpeciesStageRna symbol
    cell lineage spermatocytes
    cell lines
    at STAGE
    cell cycle     cell cycle, interphase, G1, S, G2, M
  • seven RecQ helicase domains (BLM helicase)
  • an acidic motif and two putative nuclear localization signals (NLS), in the C terminus
  • C-terminal domain is essential for strand annealing and a 60 AA stretch is important for both ssDNA binding and strand annealing
  • helicase and RNaseD C-terminal (HRDC) domain, conserved among members of the RecQ helicase family, regulating helicase activity by virtue of variations in its surface AAs, and that may be adapted for a unique function among RecQ helicases--that of bridging protein and DNA interactions
    interspecies homolog to murine Blm (77.6pc)
    intraspecies homolog to RECQL5
  • helicase family
  • RecQ subfamily
  • CATEGORY enzyme , DNA associated
    SUBCELLULAR LOCALIZATION     intracellular
    intracellular,nucleus,nucleoplasm,nuclear bodies,nuclear speckles
  • colocalizing with RPA heterotrimeric ss DNA binding protein in meiotic prophase nuclei of spermatocytes division, cell cycle, M, prophase
  • colocalizing transitorily with RPA, PML in nuclear bodies
  • present in replication fork
  • in mitotic cells, BLM and RMI2 were mostly present in the nucleoplasm
  • BLM is expressed only in dividing cells; it is absent or greatly reduced in quiescent stem cells or in terminally differentiated non-dividing cell
  • basic FUNCTION
  • DNA helicase, ATP-dependent, atypical and highly DNA structure specific, unwinding single and double strand DNA in a 3'->5' direction, promoting an ATP-dependent branch migration of Holliday junctions
  • putatively suppressor of homologous recombination between closely opposed and replicating strands, and selected target during the execution of apoptosis
  • playing a role in recombination-mediated telomere lengthening
  • DNA damage sensor signaling the formation of DNA damage induced foci
  • playing a conserved role in recovery from perturbations in DNA replication and likely RecQ helicases act to restore productive DNA replication following S-phase arrest and hence prevent subsequent genomic instability
  • playing a role in chromosome segregation in addition to its function during DNA replication and repair
  • involved in the promotion of single-stranded DNA (ssDNA) annealing
  • functioning in dissociating alternative DNA structures during recombination and/or replication at telomeric ends
  • with TOP3A execute the dissolution of sister chromatids
  • might be involved in both early and late steps of homologous recombination
  • might regress replication forks as part of a genome maintenance pathway
  • having an anti-recombination role
  • involved in disruption of the Rad51-ssDNA (single-stranded DNA) filament, an active species that promotes homologous recombination, and stimulation of DNA repair synthesis
  • playing a a role with EXO1 in the initiation of recombinational DNA repair
  • stimulating DNA strand exchange activity of RAD51 without ATP hydrolysis
  • functions as a Holliday junction dissolvase
  • role in the maintenance of gene cluster genomic integrity
  • performs double-stranded DNA unwinding by fully active duplex destabilization
  • regulates several steps of homologous recombination (HR)-dependent repair of double-strand DNA breaks
  • appears to be a master regulator that is needed by INSL6 as well as by the TOP3/RMI complex to execute diverse functions in order to maintain normal replication and genome stability
  • BRIP1 catalytic activity and its effect on BLM protein stability contribute to preservation of genomic stability and a normal response to replication stress
  • WRN and BLM are critical for maintaining genomic stability and thought to function in accurate resolution of replication blockage
  • ERCC6L and BLM decorate ultrafine histone-negative DNA threads that link the segregating sister centromeres during anaphase
  • ERCC6L and BLM limit histone association with anaphase centromeric DNA threads and promote their resolution
  • BLM and RECQL4 have coordinated activities that promote genome stability
  • ERCC6L and BLM were required for the correct recruitment to the centromere of active TOP2A, an enzyme specialized in the catenation/decatenation process
  • BLM and ERCC6L cooperate in rendering centromeric catenates accessible to TOP2A, thereby facilitating correct centromere disjunction and preventing the formation of supernumerary centromeric ultrafine anaphase bridges
  • maintains genome integrity, at least in part, by suppressing illegitimate recombination events
  • mediates a checkpoint response to stabilize the replication machinery at stalled forks, thereby preventing replisome dissociation and an irreversible fork collapse
  • possible roles of BLM helicase in the recombination-mediated mechanism of telomere elongation
  • BLM promotes DNA end resection as part of the BLM-TOP3A-RMI1-RMI2 complex
  • BLM functions in 2 distinct pathways requiring different modifications: BLM functions to suppress SCE formation and in a second pathway, its phosphorylations are essential for suppression of chromosomal radial formation
  • BLM helicase has pivotal functions at the crossroads of DNA replication, recombination, and repair
  • FANCM and BLM complex work together at stalled forks to promote both Fanconi anemia repair and replication traverse pathways of interstrand crosslinks (ICLs)
  • CELLULAR PROCESS cell life, cell death/apoptosis
    nucleotide, replication
    nucleotide, recombination
    nucleotide, repair, recombination
    nucleotide, genomic integrity
    chromosome instability pathway
    a component
  • BLM-Top3A implicated in the regulation of recombination in somatic cells
  • component of the BRCA1-associated genome surveillance complex (BASC)
  • part of a multiprotein complex that protects genome stability
  • BLM-DNA2-RPA-NBN and EXO1-BLM-RPA-NBN constitute two DNA end resection machineries for human DNA break repair
  • BLM forms the BTRR complex with topoisomerase III alpha (TOP3A) and RecQ-mediated genome instability proteins 1 and 2 (RMI1 and RMI2)
    DNA binding
    small molecule metal binding, nucleotide,
  • Mg2+
  • ATP
  • protein
  • forms a complex with DNA topoisomerase IIIalpha (TOP3A)
  • MSH1
  • MLH1 (for some aspects of genetic recombination)
  • TRF1 and TRF2 (regulating BLM activity on telomeric structures)
  • WRN
  • DNA mismatch repair protein MSH6
  • interacts with proteins involved in DNA replication, recombination, and repair and is required for the repair of stalled-replication forks and in the DNA damage response
  • interaction with RPA or WRN helicases plays an important role in the mechanism for RPA stimulation of helicase-catalyzed DNA unwinding
  • interacting with ubiquitinated FANCD2
  • interacting with RMI1
  • interacting with POLD4
  • stimulates the nucleolytic activity of exonuclease 1 (EXO1), a 5prime/3primedouble-stranded DNA exonuclease
  • interacting with XRCC3 (disruption of XRCC3 suppresses methanesulfonate and UV sensitivity and the methyl methanesulfonate- and UV-induced chromosomal aberrations of BLM cells, indicating that BLM acts downstream of XRCC3)
  • TOP3A is a type IA DNA topoisomerase that functions with BLM and RMI1 to resolve DNA replication and recombination intermediates
  • BLM and and BRIP1 were found to interact physically and functionally in human cells
  • ERCC6L binds to BLM and enables BLM localization to anaphase centromeric threads
  • SUPV3L1 interact with BLM and WRN, members of the RecQ helicase family involved in multiple DNA metabolic processes, and in protection and stabilization of the genome
  • functional relationship between BLM, ERCC6L and TOP2A in the centromere decatenation process
  • physical and functional interaction between BLM and RECQL4
  • SPIDR is the link between BLM and the HR machinery
  • SPIDR independently interacts with BLM and RAD51 and promotes the formation of a BLM/RAD51-containing complex of biological importance
  • novel role for UIMC1 in preventing proteasomal degradation of BLM in unstressed cells
  • BRCA1 and BLM interact with RAD50 predominantly in S- and G2-phases, respectively
  • WRN and BLM act epistatically with DNA2 to promote the long-range resection of double strand break ends in human cells
  • TOP3A stimulates DNA unwinding by BLM in a manner that is potentiated by RMI1-RMI2, and the processivity of resection is reliant on the TOP3A-RMI1-RMI2 complex
  • DNA2 motor promotes the enzyme capacity to degrade dsDNA in conjunction with BLM or WRN and thus promote the repair of broken DNA
  • BLM activates AKT1 and AKT1S1 to promote Prostate cancer (PC) cell proliferation and survival
  • EXO5 is epistatic to BLM at stalled replication forks, and its nuclease activity is enhanced by BLM and RPA1
  • cell & other
    activated by upregulated at the G1-S stage of the cell cycle
    RAD51L3-XRCC2 complex
    Other stimulated by single and DNA double strand breaks
    regulated by TERF1, TERF2
    negatively regulated by SUMO modification
    degraded by a proteasome-mediated pathway when BRIP1 is depleted
    corresponding disease(s) BLMS
    related resource Bloom Syndrome-BLMbase
    Other morbid association(s)
    TypeGene ModificationChromosome rearrangementProtein expressionProtein Function
    tumoral germinal mutation      
    in leukemia, lymphoma, skin tumor
    constitutional     --low  
    in G1 phase in order to promote NHEJ-mediated DNA repair, but it is stabilized by TOPBP1 in S phase cells in order to suppress sister chromatid exchange (SCE) and thereby prevent genomic instability
    Susceptibility to colorectal cancer
    Variant & Polymorphism
    Candidate gene
    Therapy target