hMre11 and hRad50 nuclear foci are induced during the normal cellular response to DNA double-strand breaks.
We previously identified a conserved multiprotein complex that includes hMre11 and hRad50. In this study, we used immunofluorescence to investigate the role of this complex in DNA double-strand break (DSB) repair. hMre11 and hRad50 form discrete nuclear foci in response to treatment with DSB-inducing agents but not in response to UV irradiation. hMre11 and hRad50 foci colocalize after treatment with ionizing radiation and are distinct from those of the DSB repair protein, hRad51. Our data indicate that an irradiated cell is competent to form either hMre11-hRad50 foci or hRad51 foci, but not both. The multiplicity of hMre11 and hRad50 foci is much higher in the DSB repair-deficient cell line 180BR than in repair-proficient cells. hMre11-hRad50 focus formation is markedly reduced in cells derived from ataxia-telangiectasia patients, whereas hRad51 focus formation is markedly increased. These experiments support genetic evidence from Saccharomyces cerevisiae indicating that Mre11-Rad50 have roles distinct from that of Rad51 in DSB repair. Further, these data indicate that hMre11-hRad50 foci form in response to DNA DSBs and are dependent upon a DNA damage-induced signaling pathway.
Maser
R S
RS
Laboratory of Genetics, University of Wisconsin Medical School, Madison 53706, USA.
Monsen
K J
KJ
Nelms
B E
BE
Petrini
J H
JH
D001260:Ataxia Telangiectasia / Q000235:genetics; D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins; D002467:Cell Nucleus / Q000737:chemistry; D002478:Cells, Cultured; D004249:DNA Damage; D004260:DNA Repair / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000032:analysis; D004706:Endodeoxyribonucleases; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005047:Etoposide / Q000494:pharmacology; D005090:Exodeoxyribonucleases; D005347:Fibroblasts / Q000528:radiation effects; D005656:Fungal Proteins / Q000032:analysis*; D016195:G2 Phase; D005720:Gamma Rays; D006801:Humans; D009154:Mutation; D017346:Protein Serine-Threonine Kinases; D011506:Proteins / Q000235:genetics; D051135:Rad51 Recombinase; D029701:Saccharomyces cerevisiae Proteins; D015398:Signal Transduction; D059005:Topoisomerase II Inhibitors; D025521:Tumor Suppressor Proteins
D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D005656:Fungal Proteins; D011506:Proteins; C086930:RAD50 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D059005:Topoisomerase II Inhibitors; D025521:Tumor Suppressor Proteins; D005047:Etoposide; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases; C495153:RAD51 protein, human; D051135:Rad51 Recombinase; D004706:Endodeoxyribonucleases; D005090:Exodeoxyribonucleases; C094191:MRE11 protein, S cerevisiae