Publication Date:
2009-07-28
Description:
Progressive telomere attrition or uncapping of the shelterin complex elicits a DNA damage response as a result of a cell's inability to distinguish dysfunctional telomeric ends from DNA double-strand breaks. Telomere deprotection activates both ataxia telangiectasia mutated (ATM) and telangiectasia and Rad3-related (ATR) kinase-dependent DNA damage response pathways, and promotes efficient non-homologous end-joining (NHEJ) of dysfunctional telomeres. The mammalian MRE11-RAD50-NBS1 (MRN; NBS1 is also known as NBN) complex interacts with ATM to sense chromosomal double-strand breaks and coordinate global DNA damage responses. Although the MRN complex accumulates at dysfunctional telomeres, it is not known whether mammalian MRN promotes repair at these sites. Here we address this question by using mouse alleles that either inactivate the entire MRN complex or eliminate only the nuclease activities of MRE11 (ref. 8). We show that cells lacking MRN do not activate ATM when telomeric repeat binding factor 2 (TRF2) is removed from telomeres, and ligase 4 (LIG4)-dependent chromosome end-to-end fusions are markedly reduced. Residual chromatid fusions involve only telomeres generated by leading strand synthesis. Notably, although cells deficient for MRE11 nuclease activity efficiently activate ATM and recruit 53BP1 (also known as TP53BP1) to deprotected telomeres, the 3' telomeric overhang persists to prevent NHEJ-mediated chromosomal fusions. Removal of shelterin proteins that protect the 3' overhang in the setting of MRE11 nuclease deficiency restores LIG4-dependent chromosome fusions. Our data indicate a critical role for the MRN complex in sensing dysfunctional telomeres, and show that in the absence of TRF2, MRE11 nuclease activity removes the 3' telomeric overhang to promote chromosome fusions. MRE11 can also protect newly replicated leading strand telomeres from NHEJ by promoting 5' strand resection to generate POT1a-TPP1-bound 3' overhangs.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2760383/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉 〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2760383/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Deng, Yibin -- Guo, Xiaolan -- Ferguson, David O -- Chang, Sandy -- K01CA124461/CA/NCI NIH HHS/ -- P30 CA046592/CA/NCI NIH HHS/ -- R01 AG028888/AG/NIA NIH HHS/ -- R01 AG028888-02/AG/NIA NIH HHS/ -- R01 CA129037/CA/NCI NIH HHS/ -- R01 CA129037-02/CA/NCI NIH HHS/ -- R01 HL079118/HL/NHLBI NIH HHS/ -- England -- Nature. 2009 Aug 13;460(7257):914-8. doi: 10.1038/nature08196. Epub 2009 Jul 26.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Genetics, Box 1010, The M.D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, Texas 77030, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19633651" target="_blank"〉PubMed〈/a〉
Keywords:
ATP-Binding Cassette Transporters/genetics/metabolism
;
Alleles
;
Animals
;
Ataxia Telangiectasia Mutated Proteins
;
Cell Cycle Proteins/genetics/metabolism
;
Cell Line
;
Chromosomal Proteins, Non-Histone
;
Chromosome Aberrations
;
DNA Damage
;
DNA Ligases/metabolism
;
DNA Repair Enzymes/deficiency/genetics/*metabolism
;
DNA-Binding Proteins/deficiency/genetics/*metabolism
;
Fibroblasts
;
Intracellular Signaling Peptides and Proteins/metabolism
;
Mice
;
Nuclear Proteins/deficiency/genetics/metabolism
;
Protein-Serine-Threonine Kinases/metabolism
;
Telomere/genetics/*metabolism
;
Telomeric Repeat Binding Protein 2/deficiency/metabolism
;
Tumor Suppressor Proteins/metabolism
Print ISSN:
0028-0836
Electronic ISSN:
1476-4687
Topics:
Biology
,
Chemistry and Pharmacology
,
Medicine
,
Natural Sciences in General
,
Physics
