| Structural highlights
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.[1] [2] [3] [4] [5] [6] [7] [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.[8] [9] [10] [11] [APLF_HUMAN] Nuclease involved in single-strand and double-strand DNA break repair. Recruited to sites of DNA damage through interaction with poly(ADP-ribose), a polymeric post-translational modification synthesized transiently at sites of chromosomal damage to accelerate DNA strand break repair reactions. Displays apurinic-apyrimidinic (AP) endonuclease and 3'-5' exonuclease activities in vitro. Also able to introduce nicks at hydroxyuracil and other types of pyrimidine base damage.[12] [13]
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[14]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ 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
- ↑ Kanno S, Kuzuoka H, Sasao S, Hong Z, Lan L, Nakajima S, Yasui A. A novel human AP endonuclease with conserved zinc-finger-like motifs involved in DNA strand break responses. EMBO J. 2007 Apr 18;26(8):2094-103. Epub 2007 Mar 29. PMID:17396150 doi:http://dx.doi.org/10.1038/sj.emboj.7601663
- ↑ Iles N, Rulten S, El-Khamisy SF, Caldecott KW. APLF (C2orf13) is a novel human protein involved in the cellular response to chromosomal DNA strand breaks. Mol Cell Biol. 2007 May;27(10):3793-803. Epub 2007 Mar 12. PMID:17353262 doi:http://dx.doi.org/MCB.02269-06
- ↑ 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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