The absence of a functional relationship between ATM and BLM, the components of BASC, in DT40 cells.
Bloom syndrome (BS) and ataxia-telangiectasia (A-T) are rare autosomal recessive diseases associated with chromosomal instability. The genes responsible for BS and A-T have been identified as BLM and ATM, respectively, whose products were recently found to be components of BRCA1-associated genome surveillance complex (BASC), a supercomplex possibly involved in the recognition and repair of aberrant DNA structures. Based on experiments using BLM(-/-) DT40 cells and BLM(-/-)/RAD54(-/-) DT40 cells, we previously suggested that BLM functions to reduce the formation of double-strand breaks (DSBs) during DNA replication. To examine whether ATM is involved in the recognition and/or repair of DSBs generated in BLM(-/-) DT40 cells and to address the functional relationship between the two BASC components, we generated BLM(-/-)/ATM(-/-) DT40 cells and characterized their properties as well as those of ATM(-/-) and BLM(-/-) DT40 cells. BLM(-/-)/ATM(-/-) cells proliferated slightly more slowly than either BLM(-/-) or ATM(-/-) cells. The sensitivity of BLM(-/-)/ATM(-/-) cells to gamma-irradiation was similar to that of ATM(-/-) cells, while BLM(-/-) cells were slightly resistant to gamma-irradiation compared with wild-type cells. BLM(-/-) cells showed sensitivity to methyl methanesulfonate (MMS) and UV irradiation while ATM(-/-) cells did not show sensitivity to either agent. The sensitivity of BLM(-/-)/ATM(-/-) cells to MMS and UV was similar to that of BLM(-/-) cells. Disrupting the function of ATM reduced the targeted integration frequency in BLM(-/-) DT40 cells. However, a defect in ATM only slightly reduced the increased sister chromatid exchanges (SCEs) in BLM(-/-) DT40 cells.
Molecular Cell Biology Laboratory, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai 980-8578, Japan.
Wensheng
W
Wang
Masayuki
M
Seki
Makoto
M
Otsuki
Shusuke
S
Tada
Noriaki
N
Takao
Ken-ichi
K
Yamamoto
Makoto
M
Hayashi
Masamitsu
M
Honma
Takemi
T
Enomoto
D000251:Adenosine Triphosphatases / Q000172:deficiency / Q000235:genetics* / Q000502:physiology; D000818:Animals; D064007:Ataxia Telangiectasia Mutated Proteins; D019313:BRCA1 Protein / Q000502:physiology; D002452:Cell Count; D018797:Cell Cycle Proteins; D002460:Cell Line / Q000473:pathology / Q000528:radiation effects; D002470:Cell Survival; D002645:Chickens; D004249:DNA Damage; D004265:DNA Helicases / Q000172:deficiency / Q000235:genetics* / Q000502:physiology; D004268:DNA-Binding Proteins; D005720:Gamma Rays; D005822:Genetic Vectors; D008741:Methyl Methanesulfonate; D017346:Protein Serine-Threonine Kinases / Q000172:deficiency / Q000235:genetics* / Q000502:physiology; D053484:RecQ Helicases; D012854:Sister Chromatid Exchange; D014162:Transfection; D025521:Tumor Suppressor Proteins; D014466:Ultraviolet Rays
D019313:BRCA1 Protein; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D025521:Tumor Suppressor Proteins; D008741:Methyl Methanesulfonate; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases; D000251:Adenosine Triphosphatases; C097151:Bloom syndrome protein; D004265:DNA Helicases; D053484:RecQ Helicases