title: Stimulation of flap endonuclease-1 by the Bloom's syndrome protein.
abstract: Bloom's syndrome (BS) is a rare autosomal recessive genetic disorder associated with genomic instability and an elevated risk of cancer. Cellular features of BS include an accumulation of abnormal replication intermediates and increased sister chromatid exchange. Although it has been suggested that the underlying defect responsible for hyper-recombination in BS cells is a temporal delay in the maturation of DNA replication intermediates, the precise role of the BS gene product, BLM, in DNA metabolism remains elusive. We report here a novel interaction of the BLM protein with the human 5'-flap endonuclease/5'-3' exonuclease (FEN-1), a genome stability factor involved in Okazaki fragment processing and DNA repair. BLM protein stimulates both the endonucleolytic and exonucleolytic cleavage activity of FEN-1 and this functional interaction is independent of BLM catalytic activity. BLM and FEN-1 are associated with each other in human nuclei as shown by their reciprocal co-immunoprecipitation from HeLa nuclear extracts. The BLM-FEN-1 physical interaction is mediated through a region of the BLM C-terminal domain that shares homology with the FEN-1 interaction domain of the Werner syndrome protein, a RecQ helicase family member homologous to BLM. This study provides the first evidence for a direct interaction of BLM with a human nucleolytic enzyme. We suggest that functional interactions between RecQ helicases and Rad2 family nucleases serve to process DNA substrates that are intermediates in DNA replication and repair.
authors.affiliation: Laboratory of Molecular Gerontology, NIA, National Institutes of Health, DHHS, Baltimore, Maryland 21224-6825, USA.
authors.forename: Sudha
authors.initials: S
authors.lastname: Sharma
authors.forename: Joshua A
authors.initials: JA
authors.lastname: Sommers
authors.forename: Leonard
authors.initials: L
authors.lastname: Wu
authors.forename: Vilhelm A
authors.initials: VA
authors.lastname: Bohr
authors.forename: Ian D
authors.initials: ID
authors.lastname: Hickson
authors.forename: Robert M
authors.initials: RM
authors.lastname: Brosh
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000688:Amylose / Q000737:chemistry; D002384:Catalysis; D002467:Cell Nucleus / Q000378:metabolism; D004247:DNA / Q000737:chemistry / Q000378:metabolism; D004265:DNA Helicases / Q000378:metabolism*; D004260:DNA Repair; D004261:DNA Replication; D004268:DNA-Binding Proteins / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004706:Endodeoxyribonucleases / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D005090:Exodeoxyribonucleases; D045585:Flap Endonucleases / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D007700:Kinetics; D008957:Models, Genetic; D009841:Oligonucleotides / Q000737:chemistry; D011233:Precipitin Tests; D011485:Protein Binding; D053484:RecQ Helicases; D011994:Recombinant Proteins / Q000737:chemistry; D011995:Recombination, Genetic; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism; D013997:Time Factors; D000071657:Werner Syndrome Helicase
chemical_list: D004268:DNA-Binding Proteins; C022262:Okazaki fragments; D009841:Oligonucleotides; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; C073998:RAD2 protein, S cerevisiae; D000688:Amylose; D004247:DNA; D004706:Endodeoxyribonucleases; D005090:Exodeoxyribonucleases; D045585:Flap Endonucleases; D000251:Adenosine Triphosphatases; C097151:Bloom syndrome protein; C506725:RECQL protein, human; D004265:DNA Helicases; D053484:RecQ Helicases; C098785:WRN protein, human; D000071657:Werner Syndrome Helicase