| Structural highlights
Disease
[NHEJ1_HUMAN] Defects in NHEJ1 are the cause of severe combined immunodeficiency due to NHEJ1 deficiency (NHEJ1-SCID) [MIM:611291]; also known as autosomal recessive T-cell-negative, B-cell-negative, NK cell-positive, severe combined immunodeficiency with microcephaly, growth retardation and sensitivity to ionizing radiation or NHEJ1 syndrome. SCID refers to a genetically and clinically heterogeneous group of rare congenital disorders characterized by impairment of both humoral and cell-mediated immunity, leukopenia and low or absent antibody levels. Patients with SCID present in infancy with recurrent, persistent infections by opportunistic organisms. The common characteristic of all types of SCID is absence of T-cell-mediated cellular immunity due to a defect in T-cell development. NHEJ1-SCID is characterized by a profound T- and B-lymphocytopenia associated with increased cellular sensitivity to ionizing radiation, microcephaly and growth retardation. Some patients may manifest SCID with sensitivity to ionizing radiation without microcephaly and mild growth retardation, probably due to hypomorphic NHEJ1 mutations.[1] [2] [3] [4] Note=A chromosomal aberration involving NHEJ1 is found in a patient with polymicrogyria. Translocation t(2;7)(q35;p22).[5]
Function
[XRCC6_HUMAN] Single stranded DNA-dependent ATP-dependent helicase. Has a role in chromosome translocation. The DNA helicase II complex binds preferentially to fork-like ends of double-stranded DNA in a cell cycle-dependent manner. It works in the 3'-5' direction. Binding to DNA may be mediated by XRCC6. Involved in DNA non-homologous end joining (NHEJ) required for double-strand break repair and V(D)J recombination. The XRCC5/6 dimer acts as regulatory subunit of the DNA-dependent protein kinase complex DNA-PK by increasing the affinity of the catalytic subunit PRKDC to DNA by 100-fold. The XRCC5/6 dimer is probably involved in stabilizing broken DNA ends and bringing them together. The assembly of the DNA-PK complex to DNA ends is required for the NHEJ ligation step. Required for osteocalcin gene expression. Probably also acts as a 5'-deoxyribose-5-phosphate lyase (5'-dRP lyase), by catalyzing the beta-elimination of the 5' deoxyribose-5-phosphate at an abasic site near double-strand breaks. 5'-dRP lyase activity allows to 'clean' the termini of abasic sites, a class of nucleotide damage commonly associated with strand breaks, before such broken ends can be joined. The XRCC5/6 dimer together with APEX1 acts as a negative regulator of transcription.[6] [7] [8] [9] [10] [11] [12] [XRCC5_HUMAN] Single stranded DNA-dependent ATP-dependent helicase. Has a role in chromosome translocation. The DNA helicase II complex binds preferentially to fork-like ends of double-stranded DNA in a cell cycle-dependent manner. It works in the 3'-5' direction. Binding to DNA may be mediated by XRCC6. Involved in DNA non-homologous end joining (NHEJ) required for double-strand break repair and V(D)J recombination. The XRCC5/6 dimer acts as regulatory subunit of the DNA-dependent protein kinase complex DNA-PK by increasing the affinity of the catalytic subunit PRKDC to DNA by 100-fold. The XRCC5/6 dimer is probably involved in stabilizing broken DNA ends and bringing them together. The assembly of the DNA-PK complex to DNA ends is required for the NHEJ ligation step. In association with NAA15, the XRCC5/6 dimer binds to the osteocalcin promoter and activates osteocalcin expression. The XRCC5/6 dimer probably also acts as a 5'-deoxyribose-5-phosphate lyase (5'-dRP lyase), by catalyzing the beta-elimination of the 5' deoxyribose-5-phosphate at an abasic site near double-strand breaks. XRCC5 probably acts as the catalytic subunit of 5'-dRP activity, and allows to 'clean' the termini of abasic sites, a class of nucleotide damage commonly associated with strand breaks, before such broken ends can be joined. The XRCC5/6 dimer together with APEX1 acts as a negative regulator of transcription.[13] [14] [15] [16] [NHEJ1_HUMAN] DNA repair protein involved in DNA nonhomologous end joining (NHEJ) required for double-strand break (DSB) repair and V(D)J recombination. May serve as a bridge between XRCC4 and the other NHEJ factors located at DNA ends, or may participate in reconfiguration of the end bound NHEJ factors to allow XRCC4 access to the DNA termini. It may act in concert with XRCC6/XRCC5 (Ku) to stimulate XRCC4-mediated joining of blunt ends and several types of mismatched ends that are noncomplementary or partially complementary.[17] [18] [19]
Publication Abstract from PubMed
The Ku70-Ku80 (Ku) heterodimer binds rapidly and tightly to the ends of DNA double-strand breaks and recruits factors of the non-homologous end-joining (NHEJ) repair pathway through molecular interactions that remain unclear. We have determined crystal structures of the Ku-binding motifs (KBM) of the NHEJ proteins APLF (A-KBM) and XLF (X-KBM) bound to a Ku-DNA complex. The two KBM motifs bind remote sites of the Ku80 alpha/beta domain. The X-KBM occupies an internal pocket formed by an unprecedented large outward rotation of the Ku80 alpha/beta domain. We observe independent recruitment of the APLF-interacting protein XRCC4 and of XLF to laser-irradiated sites via binding of A- and X-KBMs, respectively, to Ku80. Finally, we show that mutation of the X-KBM and A-KBM binding sites in Ku80 compromises both the efficiency and accuracy of end joining and cellular radiosensitivity. A- and X-KBMs may represent two initial anchor points to build the intricate interaction network required for NHEJ.
XLF and APLF bind Ku80 at two remote sites to ensure DNA repair by non-homologous end joining.,Nemoz C, Ropars V, Frit P, Gontier A, Drevet P, Yu J, Guerois R, Pitois A, Comte A, Delteil C, Barboule N, Legrand P, Baconnais S, Yin Y, Tadi S, Barbet-Massin E, Berger I, Le Cam E, Modesti M, Rothenberg E, Calsou P, Charbonnier JB Nat Struct Mol Biol. 2018 Oct;25(10):971-980. doi: 10.1038/s41594-018-0133-6., Epub 2018 Oct 5. PMID:30291363[20]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Buck D, Malivert L, de Chasseval R, Barraud A, Fondaneche MC, Sanal O, Plebani A, Stephan JL, Hufnagel M, le Deist F, Fischer A, Durandy A, de Villartay JP, Revy P. Cernunnos, a novel nonhomologous end-joining factor, is mutated in human immunodeficiency with microcephaly. Cell. 2006 Jan 27;124(2):287-99. PMID:16439204 doi:S0092-8674(06)00002-X
- ↑ Ahnesorg P, Smith P, Jackson SP. XLF interacts with the XRCC4-DNA ligase IV complex to promote DNA nonhomologous end-joining. Cell. 2006 Jan 27;124(2):301-13. PMID:16439205 doi:S0092-8674(06)00003-1
- ↑ Lu H, Pannicke U, Schwarz K, Lieber MR. Length-dependent binding of human XLF to DNA and stimulation of XRCC4.DNA ligase IV activity. J Biol Chem. 2007 Apr 13;282(15):11155-62. Epub 2007 Feb 21. PMID:17317666 doi:M609904200
- ↑ Dai Y, Kysela B, Hanakahi LA, Manolis K, Riballo E, Stumm M, Harville TO, West SC, Oettinger MA, Jeggo PA. Nonhomologous end joining and V(D)J recombination require an additional factor. Proc Natl Acad Sci U S A. 2003 Mar 4;100(5):2462-7. Epub 2003 Feb 25. PMID:12604777 doi:10.1073/pnas.0437964100
- ↑ Dai Y, Kysela B, Hanakahi LA, Manolis K, Riballo E, Stumm M, Harville TO, West SC, Oettinger MA, Jeggo PA. Nonhomologous end joining and V(D)J recombination require an additional factor. Proc Natl Acad Sci U S A. 2003 Mar 4;100(5):2462-7. Epub 2003 Feb 25. PMID:12604777 doi:10.1073/pnas.0437964100
- ↑ Reeves WH, Sthoeger ZM. Molecular cloning of cDNA encoding the p70 (Ku) lupus autoantigen. J Biol Chem. 1989 Mar 25;264(9):5047-52. PMID:2466842
- ↑ Chung U, Igarashi T, Nishishita T, Iwanari H, Iwamatsu A, Suwa A, Mimori T, Hata K, Ebisu S, Ogata E, Fujita T, Okazaki T. The interaction between Ku antigen and REF1 protein mediates negative gene regulation by extracellular calcium. J Biol Chem. 1996 Apr 12;271(15):8593-8. PMID:8621488
- ↑ Tuteja N, Tuteja R, Ochem A, Taneja P, Huang NW, Simoncsits A, Susic S, Rahman K, Marusic L, Chen J, et al.. Human DNA helicase II: a novel DNA unwinding enzyme identified as the Ku autoantigen. EMBO J. 1994 Oct 17;13(20):4991-5001. PMID:7957065
- ↑ West RB, Yaneva M, Lieber MR. Productive and nonproductive complexes of Ku and DNA-dependent protein kinase at DNA termini. Mol Cell Biol. 1998 Oct;18(10):5908-20. PMID:9742108
- ↑ Willis DM, Loewy AP, Charlton-Kachigian N, Shao JS, Ornitz DM, Towler DA. Regulation of osteocalcin gene expression by a novel Ku antigen transcription factor complex. J Biol Chem. 2002 Oct 4;277(40):37280-91. Epub 2002 Jul 26. PMID:12145306 doi:http://dx.doi.org/10.1074/jbc.M206482200
- ↑ Liu H, Herrmann CH, Chiang K, Sung TL, Moon SH, Donehower LA, Rice AP. 55K isoform of CDK9 associates with Ku70 and is involved in DNA repair. Biochem Biophys Res Commun. 2010 Jun 25;397(2):245-50. doi:, 10.1016/j.bbrc.2010.05.092. Epub 2010 May 20. PMID:20493174 doi:10.1016/j.bbrc.2010.05.092
- ↑ Roberts SA, Strande N, Burkhalter MD, Strom C, Havener JM, Hasty P, Ramsden DA. Ku is a 5'-dRP/AP lyase that excises nucleotide damage near broken ends. Nature. 2010 Apr 22;464(7292):1214-7. doi: 10.1038/nature08926. Epub 2010 Apr 11. PMID:20383123 doi:http://dx.doi.org/10.1038/nature08926
- ↑ Tuteja N, Tuteja R, Ochem A, Taneja P, Huang NW, Simoncsits A, Susic S, Rahman K, Marusic L, Chen J, et al.. Human DNA helicase II: a novel DNA unwinding enzyme identified as the Ku autoantigen. EMBO J. 1994 Oct 17;13(20):4991-5001. PMID:7957065
- ↑ Chung U, Igarashi T, Nishishita T, Iwanari H, Iwamatsu A, Suwa A, Mimori T, Hata K, Ebisu S, Ogata E, Fujita T, Okazaki T. The interaction between Ku antigen and REF1 protein mediates negative gene regulation by extracellular calcium. J Biol Chem. 1996 Apr 12;271(15):8593-8. PMID:8621488
- ↑ Willis DM, Loewy AP, Charlton-Kachigian N, Shao JS, Ornitz DM, Towler DA. Regulation of osteocalcin gene expression by a novel Ku antigen transcription factor complex. J Biol Chem. 2002 Oct 4;277(40):37280-91. Epub 2002 Jul 26. PMID:12145306 doi:http://dx.doi.org/10.1074/jbc.M206482200
- ↑ Roberts SA, Strande N, Burkhalter MD, Strom C, Havener JM, Hasty P, Ramsden DA. Ku is a 5'-dRP/AP lyase that excises nucleotide damage near broken ends. Nature. 2010 Apr 22;464(7292):1214-7. doi: 10.1038/nature08926. Epub 2010 Apr 11. PMID:20383123 doi:http://dx.doi.org/10.1038/nature08926
- ↑ Buck D, Malivert L, de Chasseval R, Barraud A, Fondaneche MC, Sanal O, Plebani A, Stephan JL, Hufnagel M, le Deist F, Fischer A, Durandy A, de Villartay JP, Revy P. Cernunnos, a novel nonhomologous end-joining factor, is mutated in human immunodeficiency with microcephaly. Cell. 2006 Jan 27;124(2):287-99. PMID:16439204 doi:S0092-8674(06)00002-X
- ↑ Ahnesorg P, Smith P, Jackson SP. XLF interacts with the XRCC4-DNA ligase IV complex to promote DNA nonhomologous end-joining. Cell. 2006 Jan 27;124(2):301-13. PMID:16439205 doi:S0092-8674(06)00003-1
- ↑ Tsai CJ, Kim SA, Chu G. Cernunnos/XLF promotes the ligation of mismatched and noncohesive DNA ends. Proc Natl Acad Sci U S A. 2007 May 8;104(19):7851-6. Epub 2007 Apr 30. PMID:17470781 doi:0702620104
- ↑ Nemoz C, Ropars V, Frit P, Gontier A, Drevet P, Yu J, Guerois R, Pitois A, Comte A, Delteil C, Barboule N, Legrand P, Baconnais S, Yin Y, Tadi S, Barbet-Massin E, Berger I, Le Cam E, Modesti M, Rothenberg E, Calsou P, Charbonnier JB. XLF and APLF bind Ku80 at two remote sites to ensure DNA repair by non-homologous end joining. Nat Struct Mol Biol. 2018 Oct;25(10):971-980. doi: 10.1038/s41594-018-0133-6., Epub 2018 Oct 5. PMID:30291363 doi:http://dx.doi.org/10.1038/s41594-018-0133-6
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