Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Bloom syndrome is a rare autosomal recessive genetic disorder characterized by growth deficiency, unusual facies, sun-sensitive telangiectatic erythema, immunodeficiency and predisposition to cancer. The causative gene for Bloom syndrome is BLM, which encodes the BLM RecQ helicase homolog protein. The first part of this review describes a long-term follow-up study of two Bloom syndrome siblings. Subsequently, the focus is placed on the functional domains of BLM. Laboratory diagnosis of Bloom syndrome by detecting mutations in BLM is laborious and impractical, unless there are common mutations in a population. Immunoblot and immunohistochemical analyses for the detection of the BLM protein using a polyclonal BLM antibody, which are useful approaches for clinical diagnosis of Bloom syndrome, are also described. In addition, a useful adjunct for the diagnosis of Bloom syndrome in terms of the BLM function is investigated, since disease cells must have the defective BLM helicase function. This review also discusses the nuclear localization signal of BLM, the proteins that interact with BLM and tumors originating from Bloom syndrome.
Expert Rev Mol Diagn 2004 May
PMID:Clinical features of Bloom syndrome and function of the causative gene, BLM helicase. 1513 5

Bloom's syndrome (BS) is a genomic instability disorder characterized by cancer susceptibility. The protein defective in BS, BLM, belongs to the RecQ family of DNA helicases. In this study, we found that BLM interacts with hp150, the largest subunit of chromatin assembly factor 1 (CAF-1), in vitro and in vivo. Colocalization of a proportion of the cellular complement of these two proteins is found at specific nuclear foci coinciding with sites of DNA synthesis in the S phase. This colocalization increases in the presence of agents that damage DNA or inhibit DNA replication. In support of a functional interaction between BLM and CAF-1, we show that BLM inhibits CAF-1-mediated chromatin assembly during DNA repair in vitro. Although CAF-1 activity is not altered in BLM-deficient cells, the absence of BLM does impair the ability of CAF-1 to be mobilized within the nucleus in response to hydroxyurea treatment. Our results provide the first link between BLM and chromatin assembly coupled to DNA repair and suggest that BLM and CAF-1 function in a coordinated way to promote survival in response to DNA damage and/or replication blockade.
Mol Cell Biol 2004 Jun
PMID:Physical and functional interaction between the Bloom's syndrome gene product and the largest subunit of chromatin assembly factor 1. 1514 66

Bloom's syndrome (BS) is an autosomal-recessive human disorder caused by mutations in the BS RecQ helicase and is associated with loss of genomic integrity and an increased incidence of cancer. We analyzed the mitotic and the meiotic roles of Caenorhabditis elegans him-6, which we show to encode the ortholog of the human BS gene. Mutations in him-6 result in an enhanced irradiation sensitivity, a partially defective S-phase checkpoint, and in reduced levels of DNA-damage induced apoptosis. Furthermore, him-6 mutants exhibit a decreased frequency of meiotic recombination that is probably due to a defect in the progression of crossover recombination. In mitotically proliferating germ cells, our genetic interaction studies, as well as the assessment of the number of double-strand breaks via RAD-51 foci, reveal a complex regulatory network that is different from the situation in yeast. Although the number of double-strand breaks in him-6 and top-3 single mutants is elevated, the combined depletion of him-6 and top-3 leads to mitotic catastrophe concomitant with a massive increase in the level of double-strand breaks, a phenotype that is completely suppressed by rad-51. him-6 and top-3 are thus needed to maintain low levels of double-strand breaks in normally proliferating germ cells, and both act in partial redundant pathways downstream of rad-51 to prevent mitotic catastrophy. Finally, we show that topoisomerase IIIalpha acts independently during a late stage of meiotic recombination.
Mol Cell Biol 2004 Jun
PMID:Multiple genetic pathways involving the Caenorhabditis elegans Bloom's syndrome genes him-6, rad-51, and top-3 are needed to maintain genome stability in the germ line. 1514 92

In addition to increased DNA-strand exchange, a cytogenetic feature of cells lacking the RecQ-like BLM helicase is a tendency for telomeres to associate. We also report additional cellular and biochemical evidence for the role of BLM in telomere maintenance. BLM co-localizes and complexes with the telomere repeat protein TRF2 in cells that employ the recombination-mediated mechanism of telomere lengthening known as ALT (alternative lengthening of telomeres). BLM co-localizes with TRF2 in foci actively synthesizing DNA during late S and G2/M; co-localization increases in late S and G2/M when ALT is thought to occur. Additionally, TRF1 and TRF2 interact directly with BLM and regulate BLM unwinding activity in vitro. Whereas TRF2 stimulates BLM unwinding of telomeric and non-telomeric substrates, TRF1 inhibits BLM unwinding of telomeric substrates only. Finally, TRF2 stimulates BLM unwinding with equimolar concentrations of TRF1, but not when TRF1 is added in molar excess. These data suggest a function for BLM in recombination-mediated telomere lengthening and support a model for the coordinated regulation of BLM activity at telomeres by TRF1 and TRF2.
Hum Mol Genet 2004 Sep 01
PMID:Association and regulation of the BLM helicase by the telomere proteins TRF1 and TRF2. 1522 85

Werner syndrome is a genetic disorder characterized by genomic instability, elevated recombination and replication defects. The WRN gene encodes a RecQ helicase whose function(s) in cellular DNA metabolism is not well understood. To investigate the role of WRN in replication, we examined its ability to rescue cellular phenotypes of a yeast dna2 mutant defective in a helicase-endonuclease that participates with flap endonuclease 1 (FEN-1) in Okazaki fragment processing. Genetic complementation studies indicate that human WRN rescues dna2-1 mutant phenotypes of growth, cell cycle arrest and sensitivity to the replication inhibitor hydroxyurea or DNA damaging agent methylmethane sulfonate. A conserved non-catalytic C-terminal domain of WRN was sufficient for genetic rescue of dna2-1 mutant phenotypes. WRN and yeast FEN-1 were reciprocally co-immunoprecipitated from extracts of transformed dna2-1 cells. A physical interaction between yeast FEN-1 and WRN is demonstrated by yeast FEN-1 affinity pull-down experiments using transformed dna2-1 cells extracts and by ELISA assays with purified recombinant proteins. Biochemical analyses demonstrate that the C-terminal domain of WRN or BLM stimulates FEN-1 cleavage of its proposed physiological substrates during replication. Collectively, the results suggest that the WRN-FEN-1 interaction is biologically important in DNA metabolism and are consistent with a role of the conserved non-catalytic domain of a human RecQ helicase in DNA replication intermediate processing.
Hum Mol Genet 2004 Oct 01
PMID:In vivo function of the conserved non-catalytic domain of Werner syndrome helicase in DNA replication. 1528 7

Bloom syndrome (BS) is a rare autosomal recessive genetic disorder characterized by lupus-like erythematous facial telangiectasia, sun sensitivity, infertility, stunted growth and a high predisposition to various types of cancer. Chromosomal abnormalities are hallmarks of this disorder, and high frequencies of sister chromatid exchanges and quadriradial configurations in lymphocytes and fibroblasts are diagnostic features. BLM is the causative gene for BS. We investigated the mutation in the BLM gene in 4 Japanese BS kindreds. Taken together with previously documented mutations, 2 kindreds were homozygous for 631delCAA and 2 were compound heterozygous for 631delCAA. The silent mutation of A1055C (Thr to Thr) was detected in control Japanese individuals. The 6-bp deletion/7-bp insertion at position 2,281, which most Askenazi Jewish BS patients carry, was not detected in 200 Japanese alleles. These results suggest that 631delCAA is a relatively common mutation among the Japanese BS patients.
Int J Mol Med 2004 Sep
PMID:Relatively common mutations of the Bloom syndrome gene in the Japanese population. 1528 97

The Rothmund-Thomson syndrome (growth retardation, skin and bone defects, predisposition to cancer) and the RAPADILINO syndrome are caused by mutations in the RECQL4 gene. The 133 kDa RECQL4 is a putative DNA helicase, a member of the family that includes the BLM and WRN helicases. The latter are mutated, respectively, in the Bloom and Werner syndromes, whose manifestations include predisposition to cancer. Using antibodies to human RECQL4, we found that the bulk of RECQL4 was present in a cytoplasmic extract of HeLa cells, in contrast to the largely nuclear BLM and WRN helicases. However, in untransformed WI-38 fibroblasts, RECQL4 was found to be largely nuclear, and was present at significantly lower total levels than in transformed HeLa cells. RECQL4 from HeLa cells was isolated as a stable complex with UBR1 and UBR2. These 200 kDa proteins are ubiquitin ligases of the N-end rule pathway, whose substrates include proteins with destabilizing N-terminal residues. The functions of this proteolytic pathway include the regulation of peptide import, chromosome stability, meiosis, apoptosis and cardiovascular development. Although the known role of UBR1 and UBR2 is to mediate polyubiquitylation (and subsequent degradation) of their substrates, the UBR1/2-bound RECQL4 was not ubiquitylated in vivo, and was a long-lived protein in HeLa cells. The isolated RECQL4-UBR1/2 complex had a DNA-stimulated ATPase activity, but was inactive in DNA-based assays for helicases and translocases, the assays in which the BLM helicase was active. We discuss ramifications of these results, possible functions of RECQL4, and the involvement of the N-end rule pathway.
Hum Mol Genet 2004 Oct 15
PMID:RECQL4, mutated in the Rothmund-Thomson and RAPADILINO syndromes, interacts with ubiquitin ligases UBR1 and UBR2 of the N-end rule pathway. 1531 57

The Werner and Bloom syndromes are caused by loss-of-function mutations in WRN and BLM, respectively, which encode the RecQ family DNA helicases WRN and BLM, respectively. Persons with Werner syndrome displays premature aging of the skin, vasculature, reproductive system, and bone, and those with Bloom syndrome display more limited features of aging, including premature menopause; both syndromes involve genome instability and increased cancer. The proteins participate in recombinational repair of stalled replication forks or DNA breaks, but the precise functions of the proteins that prevent rapid aging are unknown. Accumulating evidence points to telomeres as targets of WRN and BLM, but the importance in vivo of the proteins in telomere biology has not been tested. We show that Wrn and Blm mutations each accentuate pathology in later-generation mice lacking the telomerase RNA template Terc, including acceleration of phenotypes characteristic of latest-generation Terc mutants. Furthermore, pathology not observed in Terc mutants but similar to that observed in Werner syndrome and Bloom syndrome, such as bone loss, was observed. The pathology was accompanied by enhanced telomere dysfunction, including end-to-end chromosome fusions and greater loss of telomere repeat DNA compared with Terc mutants. These findings indicate that telomere dysfunction may contribute to the pathogenesis of Werner syndrome and Bloom syndrome.
Mol Cell Biol 2004 Oct
PMID:Telomere shortening exposes functions for the mouse Werner and Bloom syndrome genes. 1536 65

The Schizosaccharomyces pombe rqh1+ gene encodes a member of the RecQ DNA helicase family. Members of this protein family are essential for the maintenance of genetic integrity. Thus, mutations in the genes encoding the human RecQ homologues Blm, Wrn and RecQ4 cause Bloom syndrome, Werner syndrome and Rothmund-Thomson syndrome, respectively-diseases which result from genome instability. S. pombe cells that lack a functional rqh1+ gene show reduced viability and display defective chromosome segregation, particularly after UV irradiation or S-phase arrest. In this study we used an rqh1+ deletion series to show that the N-terminal portion of Rqh1 is essential for Rqh1 function. Moreover, the conserved Helicase and RNaseD C-terminal (HRDC) domain of Rqh1 also plays a role in allowing cells to tolerate exposure to DNA damaging agents and the S-phase inhibitor hydroxyurea (HU). We also demonstrate that Topoisomerase III (Top3) binds to a site within the first 322 N-terminal amino acids of Rqh1 and that this binding correlates with Rqh1 function. Genetic analysis of rqh1- top3delta mutants reveals that, in the presence of functional or partially functional Rqh1 protein, Top3 is required to maintain genome integrity and cell viability.
Mol Genet Genomics 2005 Mar
PMID:The N-terminal region of the Schizosaccharomyces pombe RecQ helicase, Rqh1p, physically interacts with Topoisomerase III and is required for Rqh1p function. 1570 47

The product of the BLM gene, which is mutated in Bloom syndrome in humans, and the Saccharomyces cerevisiae protein Sgs1 are both homologous to the Escherichia coli DNA helicase RecQ, and have been shown to be involved in the regulation of homologous recombination. Mutations in these genes result in genome instability because they increase the incidence of deletions and translocations. We present evidence for a genetic interaction between SGS1 and YKU70, which encodes the S. cerevisiae homologue of the human DNA helicase Ku70. In a yku70 mutant background, sgs1 mutations increased sensitivity to DNA breakage induced either by treatment with camptothecin or by the expression of the restriction enzyme EcoRI. The yku70 mutation caused a fourfold increase in the rate of double-strand break (DSB)-induced target integration as that seen in the sgs1 mutant. The combination of yku70 and sgs1 mutations additively increased the rate of the targeted integration, and this effect was completely suppressed by deletion of RAD51. Interestingly, an extra copy of YKU70 partially suppressed the increase in targeted integration seen in the sgs1 single mutant. These results suggest that Yku70 modulates the repair of DSBs associated with homologous recombination in a different way from Sgs1, and that the inactivation of RecQ and Ku70 homologues may enhance the frequency of gene targeting in higher eukaryotes.
Mol Genet Genomics 2005 Apr
PMID:Regulation of homologous integration in yeast by the DNA repair proteins Ku70 and RecQ. 1580 20


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