Possible association of BLM in decreasing DNA double strand breaks during DNA replication.
Bloom's syndrome (BS) is a rare genetic disorder and the cells from BS patients show genomic instability and an increased level of sister chromatid exchange (SCE). We generated BLM(-/-) and BLM(-/-)/RAD54(-/-) DT40 cells from the chicken B-lymphocyte line DT40. The BLM(-/-) DT40 cells showed higher sensitivity to methyl methanesulfonate and elevated levels of SCE as expected. The targeted integration frequency was also increased remarkably in BLM(-/-) cells. The SCE frequency increase in BLM(-/-) cells was considerably reduced and the enhanced targeted integration observed in BLM(-/-) cells was almost completely abolished in BLM(-/-)/RAD54(-/-) cells, indicating that a large portion of the SCE in BLM(-/-) cells occurs via homologous recombination, and homologous recombination events increase with the defect of BLM function. The BLM(-/-)/RAD54(-/-) cells showed a slow growth phenotype and an increased incidence of chromosome-type breaks/gaps while each single mutant showed relatively small numbers of chromosome-type breaks/gaps.
Wang
W
W
Molecular Cell Biology Laboratory, Graduate School of Pharmaceutical Sciences, Tohoku University, Aoba, Aramaki, Aoba-ku, Sendai.
Seki
M
M
Narita
Y
Y
Sonoda
E
E
Takeda
S
S
Yamada
K
K
Masuko
T
T
Katada
T
T
Enomoto
T
T
D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001816:Bloom Syndrome / Q000378:metabolism; D002166:Camptothecin / Q000494:pharmacology; D002453:Cell Cycle; D002478:Cells, Cultured; D002645:Chickens; D002869:Chromosome Aberrations; D004249:DNA Damage; D004265:DNA Helicases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017931:DNA Primers; D045643:DNA Repair Enzymes; D004261:DNA Replication; D005047:Etoposide / Q000494:pharmacology; D005656:Fungal Proteins / Q000235:genetics; D008741:Methyl Methanesulfonate / Q000494:pharmacology; D008969:Molecular Sequence Data; D053484:RecQ Helicases; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid
D017931:DNA Primers; D005656:Fungal Proteins; D029701:Saccharomyces cerevisiae Proteins; D005047:Etoposide; D008741:Methyl Methanesulfonate; D000251:Adenosine Triphosphatases; C097151:Bloom syndrome protein; C075468:RAD54 protein, S cerevisiae; D004265:DNA Helicases; D053484:RecQ Helicases; D045643:DNA Repair Enzymes; D002166:Camptothecin