Effects of double-strand break repair proteins on vertebrate telomere structure.
Although telomeres are not recognized as double-strand breaks (DSBs), some DSB repair proteins are present at telomeres and are required for telomere maintenance. To learn more about the telomeric function of proteins from the homologous recombination (HR) and non-homologous end joining pathways (NHEJ), we have screened a panel of chicken DT40 knockout cell lines for changes in telomere structure. In contrast to what has been observed in Ku-deficient mice, we found that Ku70 disruption did not result in telomere-telomere fusions and had no effect on telomere length or the structure of the telomeric G-strand overhang. G-overhang length was increased by Rad51 disruption but unchanged by disruption of DNA-PKcs, Mre11, Rad52, Rad54, XRCC2 or XRCC3. The effect of Rad51 depletion was unexpected because gross alterations in telomere structure have not been detected in yeast HR mutants. Thus, our results indicate that Rad51 has a previously undiscovered function at vertebrate telomeres. They also indicate that Mre11 is not required to generate G-overhangs. Although Mre11 has been implicated in overhang generation, overhang structure had not previously been examined in Mre11-deficient cells. Overall our findings indicate that there are significant species-specific differences in the telomeric function of DSB repair proteins.
Wei
Chao
C
Department of Molecular Genetics, Biochemistry and Microbiology, College of Medicine, University of Cincinnati, ML0524, 231 Albert Sabin Way, Cincinnati, OH 45267, USA.
Skopp
Rose
R
Takata
Minoru
M
Takeda
Shunichi
S
Price
Carolyn M
CM
D000818:Animals; D034961:Antigens, Nuclear; D030161:Avian Proteins; D002460:Cell Line; D004265:DNA Helicases; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000172:deficiency / Q000235:genetics*; D017353:Gene Deletion; D006801:Humans; D000072200:Ku Autoantigen; D000076228:MRE11 Homologue Protein; D009154:Mutation; D009687:Nuclear Proteins / Q000172:deficiency / Q000235:genetics; D051135:Rad51 Recombinase; D029701:Saccharomyces cerevisiae Proteins; D016615:Telomere / Q000235:genetics* / Q000378:metabolism
D034961:Antigens, Nuclear; D030161:Avian Proteins; D004268:DNA-Binding Proteins; C121766:MRE11 protein, human; D009687:Nuclear Proteins; D029701:Saccharomyces cerevisiae Proteins; C081647:high affinity DNA-binding factor, S cerevisiae; C495150:RAD51 protein, Gallus gallus; C495153:RAD51 protein, human; D051135:Rad51 Recombinase; D000076228:MRE11 Homologue Protein; D004265:DNA Helicases; C103532:RAD54L protein, human; C106893:XRCC5 protein, human; C000606509:Xrcc6 protein, human; C000606510:Xrcc6 protein, mouse; D000072200:Ku Autoantigen