| Structural highlights
Disease
[NBN_HUMAN] Nijmegen breakage syndrome;Hereditary breast and ovarian cancer syndrome;Familial prostate cancer. The disease is caused by mutations affecting the gene represented in this entry. Disease susceptibility is associated with variations affecting the gene represented in this entry. Disease susceptibility may be associated with variations affecting the gene represented in this entry. Defects in NBN might play a role in the pathogenesis of childhood acute lymphoblastic leukemia (ALL).[1]
Function
[TERF2_HUMAN] Binds the telomeric double-stranded 5'-TTAGGG-3' repeat and plays a central role in telomere maintenance and protection against end-to-end fusion of chromosomes. In addition to its telomeric DNA-binding role, required to recruit a number of factors and enzymes required for telomere protection, including the shelterin complex, TERF2IP/RAP1 and DCLRE1B/Apollo. Component of the shelterin complex (telosome) that is involved in the regulation of telomere length and protection. Shelterin associates with arrays of double-stranded 5'-TTAGGG-3' repeats added by telomerase and protects chromosome ends; without its protective activity, telomeres are no longer hidden from the DNA damage surveillance and chromosome ends are inappropriately processed by DNA repair pathways. Together with DCLRE1B/Apollo, plays a key role in telomeric loop (T loop) formation by generating 3' single-stranded overhang at the leading end telomeres: T loops have been proposed to protect chromosome ends from degradation and repair. Required both to recruit DCLRE1B/Apollo to telomeres and activate the exonuclease activity of DCLRE1B/Apollo. Preferentially binds to positive supercoiled DNA. Together with DCLRE1B/Apollo, required to control the amount of DNA topoisomerase (TOP1, TOP2A and TOP2B) needed for telomere replication during fork passage and prevent aberrant telomere topology. Recruits TERF2IP/RAP1 to telomeres, thereby participating in to repressing homology-directed repair (HDR), which can affect telomere length.[2] [3] [4] [NBN_HUMAN] Component of the MRE11-RAD50-NBN (MRN complex) which plays a critical role in the cellular response to DNA damage and the maintenance of chromosome integrity. The complex is involved in double-strand break (DSB) repair, DNA recombination, maintenance of telomere integrity, cell cycle checkpoint control and meiosis. The complex possesses single-strand endonuclease activity and double-strand-specific 3'-5' exonuclease activity, which are provided by MRE11. RAD50 may be required to bind DNA ends and hold them in close proximity. NBN modulate the DNA damage signal sensing by recruiting PI3/PI4-kinase family members ATM, ATR, and probably DNA-PKcs to the DNA damage sites and activating their functions. It can also recruit MRE11 and RAD50 to the proximity of DSBs by an interaction with the histone H2AX. NBN also functions in telomere length maintenance by generating the 3' overhang which serves as a primer for telomerase dependent telomere elongation. NBN is a major player in the control of intra-S-phase checkpoint and there is some evidence that NBN is involved in G1 and G2 checkpoints. The roles of NBS1/MRN encompass DNA damage sensor, signal transducer, and effector, which enable cells to maintain DNA integrity and genomic stability. Forms a complex with RBBP8 to link DNA double-strand break sensing to resection. Enhances AKT1 phosphorylation possibly by association with the mTORC2 complex.[5] [6] [7] [8] [9]
Publication Abstract from PubMed
Telomeres employ TRF2 to protect chromosome ends from activating the DNA damage sensor MRE11-RAD50-NBS1 (MRN), thereby repressing ATM-dependent DNA damage checkpoint responses. How TRF2 prevents MRN activation at dysfunctional telomeres is unclear. Here, we show that the phosphorylation status of NBS1 determines the repair pathway choice of dysfunctional telomeres. The crystal structure of the TRF2-NBS1 complex at 3.0 A resolution shows that the NBS1 429YQLSP433 motif interacts specifically with the TRF2TRFH domain. Phosphorylation of NBS1 serine 432 by CDK2 in S/G2 dissociates NBS1 from TRF2, promoting TRF2-Apollo/SNM1B complex formation and the protection of leading-strand telomeres. Classical-NHEJ-mediated repair of telomeres lacking TRF2 requires phosphorylated NBS1S432 to activate ATM, while interaction of de-phosphorylated NBS1S432 with TRF2 promotes alternative-NHEJ repair of telomeres lacking POT1-TPP1. Our work advances understanding of how the TRF2TRFH domain orchestrates telomere end protection and reveals how the phosphorylation status of the NBS1S432 dictates repair pathway choice of dysfunctional telomeres.
NBS1 Phosphorylation Status Dictates Repair Choice of Dysfunctional Telomeres.,Rai R, Hu C, Broton C, Chen Y, Lei M, Chang S Mol Cell. 2017 Mar 2;65(5):801-817.e4. doi: 10.1016/j.molcel.2017.01.016. Epub, 2017 Feb 16. PMID:28216226[10]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Varon R, Reis A, Henze G, von Einsiedel HG, Sperling K, Seeger K. Mutations in the Nijmegen Breakage Syndrome gene (NBS1) in childhood acute lymphoblastic leukemia (ALL). Cancer Res. 2001 May 1;61(9):3570-2. PMID:11325820
- ↑ van Steensel B, Smogorzewska A, de Lange T. TRF2 protects human telomeres from end-to-end fusions. Cell. 1998 Feb 6;92(3):401-13. PMID:9476899
- ↑ de Lange T. Shelterin: the protein complex that shapes and safeguards human telomeres. Genes Dev. 2005 Sep 15;19(18):2100-10. PMID:16166375 doi:10.1101/gad.1346005
- ↑ Ye J, Lenain C, Bauwens S, Rizzo A, Saint-Leger A, Poulet A, Benarroch D, Magdinier F, Morere J, Amiard S, Verhoeyen E, Britton S, Calsou P, Salles B, Bizard A, Nadal M, Salvati E, Sabatier L, Wu Y, Biroccio A, Londono-Vallejo A, Giraud-Panis MJ, Gilson E. TRF2 and apollo cooperate with topoisomerase 2alpha to protect human telomeres from replicative damage. Cell. 2010 Jul 23;142(2):230-42. doi: 10.1016/j.cell.2010.05.032. PMID:20655466 doi:10.1016/j.cell.2010.05.032
- ↑ Zhu XD, Kuster B, Mann M, Petrini JH, de Lange T. Cell-cycle-regulated association of RAD50/MRE11/NBS1 with TRF2 and human telomeres. Nat Genet. 2000 Jul;25(3):347-52. PMID:10888888 doi:http://dx.doi.org/10.1038/77139
- ↑ Stiff T, Reis C, Alderton GK, Woodbine L, O'Driscoll M, Jeggo PA. Nbs1 is required for ATR-dependent phosphorylation events. EMBO J. 2005 Jan 12;24(1):199-208. Epub 2004 Dec 16. PMID:15616588 doi:http://dx.doi.org/7600504
- ↑ Yuan J, Chen J. N terminus of CtIP is critical for homologous recombination-mediated double-strand break repair. J Biol Chem. 2009 Nov 13;284(46):31746-52. doi: 10.1074/jbc.M109.023424. Epub, 2009 Sep 16. PMID:19759395 doi:10.1074/jbc.M109.023424
- ↑ Wang JQ, Chen JH, Chen YC, Chen MY, Hsieh CY, Teng SC, Wu KJ. Interaction between NBS1 and the mTOR/Rictor/SIN1 complex through specific domains. PLoS One. 2013 Jun 6;8(6):e65586. doi: 10.1371/journal.pone.0065586. Print 2013. PMID:23762398 doi:http://dx.doi.org/10.1371/journal.pone.0065586
- ↑ Trujillo KM, Yuan SS, Lee EY, Sung P. Nuclease activities in a complex of human recombination and DNA repair factors Rad50, Mre11, and p95. J Biol Chem. 1998 Aug 21;273(34):21447-50. PMID:9705271
- ↑ Rai R, Hu C, Broton C, Chen Y, Lei M, Chang S. NBS1 Phosphorylation Status Dictates Repair Choice of Dysfunctional Telomeres. Mol Cell. 2017 Mar 2;65(5):801-817.e4. doi: 10.1016/j.molcel.2017.01.016. Epub, 2017 Feb 16. PMID:28216226 doi:http://dx.doi.org/10.1016/j.molcel.2017.01.016
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