Affinage

XRCC4

DNA repair protein XRCC4 · UniProt Q13426

Length
336 aa
Mass
38.3 kDa
Annotated
2026-06-11
100 papers in source corpus 49 papers cited in narrative 46 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 8/8 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

XRCC4 is a core scaffolding protein of the non-homologous end-joining (NHEJ) pathway, required for completion of DNA double-strand break repair and V(D)J recombination (PMID:8548796, PMID:10786799). Its central function is to bind DNA ligase IV through the ligase's inter-BRCT linker and tandem BRCT region, an interaction that stabilizes ligase IV protein (which is nearly absent without XRCC4) and stimulates its ligation activity several-fold (PMID:9242410, PMID:10047779, PMID:19332554). Structurally, XRCC4 is an elongated dimer with N-terminal globular head domains and a long C-terminal coiled-coil stalk that engages ligase IV; tetramerization and ligase IV binding are mutually exclusive, defining distinct functional states (PMID:11080143, PMID:11702069, PMID:14607114). The XRCC4-ligase IV complex is recruited to broken ends by the Ku heterodimer in a DNA-stimulated manner, where it cooperates with Ku and DNA-PKcs and can ligate even incompatible or gapped ends (PMID:10757784, PMID:10854421, PMID:17290226). Through head-domain contacts XRCC4 assembles with XLF into alternating super-helical filaments that form a positively charged channel and act as mobile 'sliding sleeves' bridging and aligning two DNA ends independently of ligase IV (PMID:21775435, PMID:22287571, PMID:22228831, PMID:27437582). XRCC4 also serves as a platform recruiting end-processing enzymes — PNKP and aprataxin via CK2-phosphorylation-dependent FHA interactions, DNA polymerase lambda, WRN, and Artemis — coupling end processing to ligation (PMID:15385968, PMID:15451442, PMID:20852255, PMID:28696258). XRCC4 function is regulated by post-translational modification: SUMOylation at K210 drives nuclear accumulation, and FBXW7-mediated K63-polyubiquitylation at K296 (following DNA-PKcs phosphorylation) enhances Ku association and NHEJ efficiency (PMID:16478998, PMID:26774286). Genetically, p53 loss rescues the embryonic lethality of XRCC4 deficiency in mice, and XRCC4 contributes to immunoglobulin class switch recombination, establishing NHEJ as a genome caretaker (PMID:10786799, PMID:17606631).

Mechanistic history

Synthesis pass · year-by-year structured walk · 18 steps
  1. 1995 High

    Established that XRCC4 is genetically required to complete V(D)J recombination and double-strand break repair, defining it as an essential NHEJ factor before any molecular activity was known.

    Evidence Functional complementation of XRCC4-deficient XR-1 CHO cells with human cDNA and V(D)J/DSBR assays

    PMID:8548796

    Open questions at the time
    • Did not reveal the biochemical activity of XRCC4
    • No interaction partners identified
  2. 1997 High

    Identified DNA ligase IV as the direct partner of XRCC4 and showed XRCC4 stimulates its ligation activity, assigning XRCC4 a concrete biochemical role in end ligation.

    Evidence Co-IP, yeast two-hybrid, and in vitro ligation assay with purified proteins; mapping to the ligase IV BRCT region

    PMID:9242410 PMID:9259561 PMID:9352367

    Open questions at the time
    • Did not establish how the complex reaches DNA ends
    • Stoichiometry of the complex unresolved
  3. 1998 High

    Mapped the XRCC4–ligase IV interface to the inter-BRCT linker and demonstrated the interaction is essential for NHEJ in vivo, while showing XRCC4 stabilizes ligase IV protein.

    Evidence Deletion mapping with in vitro binding and in vivo complementation; protein/mRNA analysis in XR-1 cells

    PMID:10047779 PMID:9705934 PMID:9733770

    Open questions at the time
    • Mechanism of ligase IV stabilization not defined
    • DNA-binding role of XRCC4 still unclear
  4. 1999 High

    Showed XRCC4 binds DNA nicks and ends and possesses ligase IV-independent functions, indicating roles beyond simply stimulating the ligase.

    Evidence DNA-binding assays, adenylation assays, and complementation with deletion/mutant XRCC4

    PMID:10202163

    Open questions at the time
    • Identity of ligase IV-independent functions not defined
  5. 2000 High

    Resolved XRCC4 architecture by crystallography and reconstituted its recruitment to DNA ends via Ku and DNA-PKcs, defining how the ligation complex is positioned at breaks.

    Evidence X-ray crystallography of XRCC4; co-IP and in vitro ligation/end-binding assays with Ku, DNA-PKcs, and the XRCC4-LigIV complex; cross-linking and stoichiometry

    PMID:10757784 PMID:10854421 PMID:10945980 PMID:11080143

    Open questions at the time
    • How Ku and XRCC4 physically connect remained ambiguous
    • Dynamics of recruitment in cells not addressed
  6. 2000 High

    Demonstrated in mice that NHEJ acts as a genome caretaker, with p53 loss rescuing XRCC4-null lethality but not the recombination defect, linking XRCC4 to tumour suppression.

    Evidence XRCC4/p53 double-knockout mouse; genetic epistasis, tumour pathology, and translocation analysis

    PMID:10786799

    Open questions at the time
    • Molecular basis of apoptosis suppression by p53 loss not defined
  7. 2001 High

    Defined the atomic XRCC4–ligase IV interface and the asymmetric 2:1 binding mode, with binding inducing conformational change in XRCC4 tails.

    Evidence X-ray crystallography of XRCC4 bound to the ligase IV inter-BRCT peptide; later 2003 sedimentation analysis establishing dimer/tetramer exclusivity

    PMID:11702069 PMID:14607114

    Open questions at the time
    • Functional significance of the dimer-tetramer equilibrium in cells unresolved
  8. 2003 High

    Mapped DNA-PK phosphorylation sites on XRCC4 (S260, S318) and showed they are dispensable for survival and V(D)J recombination, ruling out these modifications as direct controllers of NHEJ.

    Evidence Mass spectrometry site mapping plus alanine mutagenesis with complementation and IR survival assays

    PMID:14599745

    Open questions at the time
    • Other phosphorylation sites and their roles not yet examined
    • Function of XRCC4 phosphorylation left open
  9. 2004 High

    Established XRCC4 as a recruitment hub for end-processing enzymes, linking PNK, aprataxin, and polymerase lambda to the ligation complex.

    Evidence Co-IP, CK2-dependent FHA-domain binding, in vitro activity and end-joining assays; siRNA disruption with IR survival/repair kinetics

    PMID:12517771 PMID:12547193 PMID:15380105 PMID:15385968 PMID:15451442 PMID:17272270

    Open questions at the time
    • Order of enzyme recruitment relative to ligation not fully defined
    • Some interactions characterized in single labs
  10. 2006 High

    Showed SUMOylation at K210 governs XRCC4 nuclear import and identified XLF and direct Ku70/80 binding as components governing complex assembly and chromatin recruitment.

    Evidence SUMO modification assays with K210R mutant and rescue; XLF co-IP and patient-cell complementation; laser micro-irradiation, FRAP, and Ku70-XRCC4 interaction assays

    PMID:12509254 PMID:16439205 PMID:16478998 PMID:16571728 PMID:17124166

    Open questions at the time
    • SUMO E3 ligase for XRCC4 not identified
    • Relative contributions of Ku-XRCC4 versus Ku-ligase IV contacts to recruitment unresolved
  11. 2007 High

    Demonstrated the catalytic versatility of XRCC4-ligase IV — joining incompatible ends and gaps — and extended XRCC4's biological role to immunoglobulin class switch recombination.

    Evidence In vitro ligation with defined incompatible/gapped substrates; conditional B-cell XRCC4 knockout with CSR assays; LigIV-Ku BRCT mapping

    PMID:17241822 PMID:17290226 PMID:17606631

    Open questions at the time
    • Mechanism of incompatible-end accommodation at structural level not defined
  12. 2008 Medium

    Extended the XRCC4-ligase IV interactome to WRN, coupling WRN exonuclease processing to downstream ligation.

    Evidence Co-IP and in vitro exonuclease/helicase and end-joining assays

    PMID:18558713

    Open questions at the time
    • Single-lab biochemistry without cellular validation
    • Physiological context of WRN-X4L4 cooperation unclear
  13. 2011 High

    Revealed that XRCC4 and XLF assemble into alternating super-helical filaments forming a positively charged DNA-binding channel, providing a structural basis for end bridging and alignment.

    Evidence Crystallography, EM, SAXS, calorimetry, and mutagenesis of XLF-XRCC4 head-domain contacts; FRAP and imaging of LigIV control of XRCC4 nuclear import

    PMID:21768349 PMID:21775435 PMID:21936820 PMID:21982441

    Open questions at the time
    • Filament length and stoichiometry on real broken DNA in cells not defined
  14. 2012 High

    Showed XRCC4-XLF bridges two DNA molecules independently of ligase IV and that this bridging is needed specifically for coding-end joining and is regulated by DNA-PK phosphorylation.

    Evidence DNA bridging assays, crystallography, separation-of-function XRCC4 mutants, and V(D)J recombination assays

    PMID:22228831 PMID:22287571

    Open questions at the time
    • Why bridging is selectively required for coding but not signal ends not explained
  15. 2016 High

    Visualized XRCC4-XLF bridges as mobile 'sliding sleeves' on single DNA molecules and identified FBXW7-mediated K63-ubiquitylation at K296 as a regulator enhancing Ku association.

    Evidence Optical tweezers with single-molecule fluorescence; in vivo ubiquitylation assays, mutagenesis, small-molecule inhibitor, and NHEJ reporter assays; SAXS of APLF-linked core complex

    PMID:26774286 PMID:27437582 PMID:27875301

    Open questions at the time
    • How sliding sleeves are converted to a static ligation-competent state unresolved
    • Deubiquitylase counteracting K296 ubiquitylation not identified
  16. 2017 High

    Defined how XRCC4-ligase IV stimulates and coordinates end-processing enzymes (PNKP, Artemis) and showed C-terminal tail phosphorylation tunes DNA bridging independently of ligation.

    Evidence SAXS/HDX of PNKP-X4L4 complex; in vitro Artemis nuclease assays; phospho-mimic mutagenesis with bridging and LigIV-stimulation assays

    PMID:28453785 PMID:28500754 PMID:28696258

    Open questions at the time
    • Temporal coupling of processing to ligation in cells not directly observed
  17. 2015 High

    Identified PAXX as an XRCC4 paralog that promotes Ku-dependent ligation and core NHEJ assembly, expanding the XRCC4-superfamily scaffold network.

    Evidence Crystal structure, co-IP, CRISPR/RNAi knockout, chromatin fractionation, and in vitro ligation

    PMID:25574025

    Open questions at the time
    • Functional redundancy/division of labour between XRCC4, XLF and PAXX incompletely resolved
  18. 2021 Medium

    Linked XRCC4 to innate immunity, with RIG-I suppressing NHEJ complex formation while XRCC4 reciprocally augments RIG-I signaling.

    Evidence Co-IP, DSB repair and innate immune signaling assays, and an in vivo viral infection model

    PMID:33846346

    Open questions at the time
    • Single-lab finding awaiting independent replication
    • Physiological significance of the XRCC4-RIG-I axis unresolved

Open questions

Synthesis pass · forward-looking unresolved questions
  • How the dynamic, sliding XRCC4-XLF filament transitions to a fixed, ligation-competent synaptic state and how the many post-translational modifications are temporally integrated during repair remain open.
  • No real-time model linking bridging, processing, and ligation steps
  • Coordination of SUMO, phosphorylation, and ubiquitylation signals over the repair cycle undefined

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0003677 DNA binding 4 GO:0060090 molecular adaptor activity 4 GO:0005198 structural molecule activity 3 GO:0098772 molecular function regulator activity 3
Localization
GO:0005634 nucleus 3 GO:0000228 nuclear chromosome 2 GO:0005829 cytosol 2
Pathway
R-HSA-73894 DNA Repair 4 R-HSA-168256 Immune System 3 R-HSA-1640170 Cell Cycle 1
Partners
APTXLIG4PAXXPNKPPRKDCXLFXRCC5XRCC6
Complex memberships
NHEJ core complex (Ku/DNA-PKcs/X4L4)XRCC4-DNA ligase IV complexXRCC4-XLF filament

Evidence

Reading pass · 46 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
1995 XRCC4 encodes a novel protein required for completion of V(D)J recombination (both coding and signal joins) and DNA double-strand break repair; XR-1 cells lacking XRCC4 can initiate but not complete V(D)J recombination, and human XRCC4 cDNA complements both defects. Functional complementation of XRCC4-deficient XR-1 CHO cells with human XRCC4 cDNA; V(D)J recombination substrate assays; DSBR sensitivity assays Cell High 8548796
1997 XRCC4 directly interacts with DNA ligase IV and stimulates its ligation activity 5–8-fold in vitro; the two proteins co-immunoprecipitate and interact in yeast two-hybrid, establishing that the primary function of XRCC4 is to stimulate DNA ligase IV for DSB ligation. Co-immunoprecipitation; yeast two-hybrid; in vitro ligation assay with purified proteins; co-expression in insect cells Nature High 9242410
1997 XRCC4 interacts with DNA ligase IV via the unique carboxy-terminal extension of ligase IV that contains tandem BRCT domains; XRCC4 and ligase IV co-purify quantitatively and XRCC4 is a nuclear phosphoprotein that is an in vitro substrate for DNA-PK. Co-immunoprecipitation; co-purification across chromatographic steps; adenylylation assay; protein mapping/deletion analysis; in vitro DNA-PK phosphorylation assay Current biology : CB High 9259561
1997 XRCC4 forms a homodimer in vivo; the homodimerization domain maps to amino acids 115–204; a core functional domain (aa 18–204) is required for V(D)J recombination; XRCC4 localizes to the nucleus. Yeast two-hybrid with deletion mutants; transient V(D)J recombination assay; nuclear localization imaging International immunology Medium 9352367
1998 DNA ligase IV binds XRCC4 via a region located between (not within) its tandem BRCT domains; this inter-BRCT linker region is necessary and sufficient for XRCC4 binding. Deletion analysis of DNA ligase IV; co-expression and co-immunoprecipitation; in vitro binding assays Current biology : CB High 9705934
1998 A central region of XRCC4 (amino acids 100–250) is required for DNA ligase IV binding; deletions within this region abolish in vivo NHEJ and V(D)J recombination, demonstrating the physical interaction with ligase IV is essential for XRCC4 function in vivo. XRCC4 deletion mutant analysis; in vitro ligase IV binding assay; in vivo complementation of XRCC4-deficient cells The Journal of biological chemistry High 9733770
1998 XRCC4 is an in vitro substrate of DNA-PK; phosphorylation occurs on serine, threonine, and tyrosine in insect cells and on serine/threonine within the C-terminal 130 aa by DNA-PK in vitro; recombinant XRCC4 facilitates Ku binding to DNA and promotes DNA-PK assembly on DNA ends. In vitro kinase assay with DNA-PK and recombinant XRCC4; phosphoamino acid analysis; DNA-binding/Ku-assembly assays The Journal of biological chemistry Medium 9430729
1998 XRCC4 stabilizes DNA ligase IV protein; in XRCC4-deficient XR-1 cells DNA ligase IV protein is nearly absent despite normal mRNA levels, and reintroduction of XRCC4 restores ligase IV to wild-type levels. Western blot; mRNA analysis by Northern/RT-PCR; XRCC4 cDNA transfection into XR-1 cells Mutation research High 10047779
1999 XRCC4 binds DNA with preference for nicks or broken ends; DNA binding of XRCC4 is correlated with V(D)J recombination complementation activity but is not required for stimulation of DNA ligase IV adenylation, indicating XRCC4 has DNA ligase IV-independent functions. DNA-binding assays with purified protein; adenylation assay for ligase IV; functional complementation assay in XRCC4-deficient cells; deletion/mutation analysis The EMBO journal High 10202163
2000 The crystal structure of XRCC4 reveals an elongated dumbbell-shaped tetramer with N-terminal globular head domains containing a beta-sandwich and helix-turn-helix motif, and a C-terminal stalk of >120 Å alpha-helix that mediates ligase IV interaction; the structure suggests coupling of ligase IV association with DNA binding. X-ray crystallography at 2.7 Å resolution The EMBO journal High 11080143
2000 XRCC4-ligase IV complex interacts directly with the Ku heterodimer in a DNA-stimulated manner; this interaction recruits XRCC4-ligase IV to DNA ends, increasing the initial ligation rate 20-fold; Ku's interaction is specific for ligase IV and does not extend to other mammalian ligases. Co-immunoprecipitation; in vitro ligation assay; DNA end-binding assay; preformation of Ku/XRCC4-LigIV complex Molecular and cellular biology High 10757784
2000 DNA ligase IV-XRCC4 complex binds specifically to ends of duplex DNA and can bridge two DNA molecules; Ku and DNA-PKcs bind simultaneously with XRCC4-LigIV at DNA ends; DNA-PKcs stimulates intermolecular ligation while Ku inhibits intramolecular ligation. DNA end-binding assays; intermolecular/intramolecular ligation assays with purified proteins; simultaneous binding experiments The Journal of biological chemistry High 10854421
2000 DNA ligase IV and XRCC4 form a stable mixed tetramer (~300 kDa, 2:2 stoichiometry) with XRCC4 homodimer at the core and ligase IV subunits not in direct contact with each other; this complex functions synergistically with Ku and DNA-PKcs in cell-free end-joining. Protein expression and purification; cross-linking; size estimation; cell-free end-joining reconstitution assay The Journal of biological chemistry Medium 10945980
2000 p53-deficiency rescues embryonic lethality and neuronal apoptosis caused by XRCC4 deficiency in mice, but does not rescue impaired V(D)J recombination; XRCC4/p53 double-deficient mice develop pro-B cell lymphomas with c-myc/IgH translocations, establishing NHEJ as a genome caretaker. Double-knockout mouse model; genetic epistasis; tumor pathology; chromosomal translocation analysis Nature High 10786799
2001 Crystal structure of human XRCC4 bound to the DNA ligase IV inter-BRCT linker peptide shows that a single ligase IV chain binds asymmetrically to an XRCC4 dimer; binding causes conformational change in XRCC4 helical tails (coiled-coil unwinds to flat surface); interaction is mediated by charged hydrogen bonds and extensive hydrophobic contacts. X-ray crystallography Nature structural biology High 11702069
2002 Direct protein-protein interactions in the NHEJ complex: ligase IV interacts with Ku via its BRCT domains; XRCC4 interacts directly with DNA-PKcs; ligase IV does not bind DNA-PKcs and XRCC4 does not bind Ku directly (or only very weakly). Pull-down assays; co-immunoprecipitation with defined protein pairs; DNA-independent interaction assays DNA repair Medium 12509254
2003 DNA-PK phosphorylates XRCC4 at serines 260 and 318 (mapped by mass spectrometry) within the C-terminal 100 aa, but these phosphorylations are not required for cell survival after IR or for V(D)J recombination, indicating these sites do not directly control NHEJ function. Mass spectrometry phosphorylation mapping; alanine-substitution mutagenesis; complementation assay in XRCC4-deficient cells; IR survival assay DNA repair High 14599745
2003 XRCC4 tetramerization and DNA ligase IV binding are mutually exclusive; only the XRCC4 dimer associates with ligase IV (2:1 stoichiometry in solution); the dimer-tetramer equilibrium likely separates two functional states of XRCC4. Equilibrium sedimentation analysis; mutational analysis of XRCC4; biochemical complex formation assays Journal of molecular biology High 14607114
2004 XRCC4 physically links polynucleotide kinase (PNK) to DNA ligase IV via a CK2-phosphorylation-dependent interaction; the PNK FHA domain binds CK2-phosphorylated XRCC4; disruption of this interaction causes increased radiosensitivity and slower DSB repair kinetics. Co-immunoprecipitation; FHA domain binding assay; in vitro end-joining assay; CK2 phosphorylation assay; siRNA disruption in cells; IR survival/repair kinetics The EMBO journal High 15385968
2004 Aprataxin (AOA1 gene product) physically interacts with XRCC4 in vitro and in vivo via its divergent FHA domain binding to CK2-phosphorylated XRCC4. Co-immunoprecipitation in vitro and in vivo; FHA domain-phosphopeptide binding analysis DNA repair Medium 15380105
2004 DNA polymerase lambda interacts with the XRCC4-DNA ligase IV complex via its N-terminal BRCT domain, and this interaction stimulates pol lambda DNA synthesis activity; pol lambda can perform gap-filling on NHEJ substrates. Co-immunoprecipitation; in vitro gap-filling synthesis assay; interaction mapping with truncated pol lambda forms Biochemical and biophysical research communications Medium 15451442
2004 Recruitment of XRCC4-ligase IV complex to DNA ends requires coordinated assembly of both Ku and DNA-PKcs (p460); interactions of Ku and p460 with XRCC4-LigIV are mainly DNA-dependent; XRCC4 is phosphorylated by DNA-PK upon recruitment but phosphorylation is not required for loading. In vitro DNA-end pull-down from nuclear extracts; co-immunoprecipitation; wortmannin inhibition; phosphorylation assay Journal of molecular biology High 12547193
2004 DNA processing for NHEJ (polymerase and nuclease activities) requires XRCC4/Ligase IV in addition to wortmannin-sensitive kinase activity; XRCC4/LigIV is required for alignment-based gap filling preceding ligation of radiation-induced DSBs. Two-stage cell-free NHEJ assay; supplementation of XRCC4-deficient extracts with recombinant XRCC4/LigIV; kinase inhibitor (wortmannin) treatment The Journal of biological chemistry; Cancer research Medium 12517771 17272270
2006 XRCC4 is SUMOylated on lysine 210; this modification is required for nuclear accumulation of XRCC4; SUMO-deficient XRCC4 (K210R) remains cytoplasmic, causes radiation sensitivity and failure to complete V(D)J recombination; genetic fusion of SUMO to the C-terminus rescues nuclear localization and function. Site-directed mutagenesis; in vitro and in vivo SUMO modification assays; subcellular fractionation/immunofluorescence; IR survival assay; V(D)J recombination assay Molecular and cellular biology High 16478998
2006 XLF (Cernunnos) directly interacts with the XRCC4-Ligase IV complex in vitro and in vivo and is required for efficient NHEJ; siRNA knockdown causes radiosensitivity and NHEJ defect; XLF is absent in patient 2BN cells due to frameshift mutation and its reintroduction corrects the defect. Co-immunoprecipitation in vitro and in vivo; siRNA knockdown; IR survival; NHEJ reporter assay; complementation of patient cells Cell High 16439205
2006 Cernunnos/XLF physically interacts with the XRCC4-DNA ligase IV complex and is the mammalian homolog of yeast Nej1, identifying it as a new component of the NHEJ ligation complex. Co-immunoprecipitation; sequence homology analysis (sensitive sequence analysis methods) The Journal of biological chemistry Medium 16571728
2006 Ku70/80 interacts directly with XRCC4; XRCC4/LigIV accumulation at DSBs depends on Ku70/80 but not DNA-PKcs; Ku heterodimers are in dynamic equilibrium at DNA ends; XRCC4 may serve as a flexible tether between Ku70/80 and ligase IV. Pulsed near-IR laser micro-irradiation; live-cell imaging; FRAP; co-immunoprecipitation; direct interaction assay (Ku70-XRCC4) Proceedings of the National Academy of Sciences of the United States of America High 17124166
2007 XRCC4-DNA ligase IV can ligate two DNA ends with fully incompatible 3' overhangs (no base pairing) and can ligate across single-nucleotide gaps; XLF stimulates joining of both compatible and incompatible ends. In vitro ligation assay with purified XRCC4-LigIV complex; defined DNA substrates with incompatible overhangs and gaps; Ku stimulation assays The EMBO journal High 17290226
2007 Ku interacts with DNA ligase IV via its first BRCT domain (residues 644–748); this interaction is enhanced by XRCC4 and dsDNA; DNA-PK kinase activity causes disassembly of the Ku/DNA ligase IV/XRCC4 complex. Co-immunoprecipitation; deletion mapping of LigIV-Ku interaction; in vitro complex formation; kinase activity assays DNA repair Medium 17241822
2007 XRCC4 plays a role in immunoglobulin class switch recombination (CSR); B-lymphocyte-restricted conditional XRCC4 knockout leads to ~2-fold reduction in CSR, implicating NHEJ in CSR resolution. Conditional knockout mouse (LoxP-flanked XRCC4, Cre-lentiviral); in vivo and in vitro CSR assays in B cells The Journal of experimental medicine High 17606631
2008 Werner protein (WRN) physically interacts with the XRCC4-DNA ligase IV complex (X4L4); X4L4 stimulates WRN exonuclease but not helicase activity; in a DNA end-joining assay, WRN-processed substrates are ligated by X4L4. Co-immunoprecipitation; in vitro exonuclease/helicase activity assays; DNA end-joining assay Biochemistry Medium 18558713
2009 High-resolution crystal structure of human XRCC4 bound to the C-terminal tandem BRCT repeat of DNA ligase IV reveals an extensive binding interface formed by a helix-loop-helix in the inter-BRCT linker and the second BRCT domain; second BRCT domain contact is necessary for stable binding in cells. X-ray crystallography (high-resolution); mutagenesis; cellular radiosensitization assays with dominant-negative LigIV fragments Molecular and cellular biology High 19332554
2010 CK2-phosphorylated XRCC4 promotes high-affinity interaction with PNKP FHA domain, stimulating PNKP turnover; unphosphorylated XRCC4 also interacts via a lower-affinity site in the PNKP catalytic domain; paradoxically, CK2-phosphorylated XRCC4 inhibits PNKP activity. Co-immunoprecipitation; in vitro FHA domain binding; PNKP kinase/phosphatase activity assays; CK2 phosphorylation assays The Journal of biological chemistry High 20852255
2011 XLF and XRCC4 form alternating super-helical filaments through head-domain interactions; XLF Leu-115 ('Leu-lock') inserts into a hydrophobic pocket on XRCC4 (Met-59, Met-61, Lys-65, Lys-99, Phe-106, Leu-108); these filaments form a positively charged channel to bind and align DNA ends for ligation. X-ray crystallography (crystal + solution structures); SAXS; site-directed mutagenesis; DNA-binding assays The Journal of biological chemistry High 21775435
2011 XLF and XRCC4 dimers interact through their N-terminal head domains to form alternating left-handed helical filaments (confirmed at 5.5 Å and 8.5 Å resolution); key XRCC4 residues Glu55, Asp58, Met61, and Phe106 are essential for interaction with XLF. X-ray crystallography; electron microscopy; calorimetry; site-directed mutagenesis Proceedings of the National Academy of Sciences of the United States of America; Biochemical Society transactions High 21768349 21936820
2011 DNA Ligase IV controls nuclear import and sub-nuclear distribution of XRCC4; in LigIV-deficient cells XRCC4 remains cytoplasmic; co-expression with LigIV restores nuclear localization of XRCC4; XRCC4/LigIV complex exchanges faster at DNA damage sites than XRCC4 alone. Fluorescent fusion protein expression; live-cell imaging; FRAP; LigIV-deficient cell line complementation DNA repair High 21982441
2012 XRCC4-XLF complexes bridge two independent DNA molecules in a LigIV-independent manner; XRCC4's interaction with XLF is required for coding (but not signal) end joining in V(D)J recombination; DNA-PK phosphorylation of XRCC4/XLF disrupts DNA bridging in vitro. DNA-binding and bridging assays; crystal structure (3.94 Å); XRCC4 mutants abolishing XLF interaction; V(D)J recombination assays; DNA-PK phosphorylation assay Nucleic acids research; Nucleic acids research High 22228831 22287571
2014 DNA Ligase IV is required for nuclear localization of XRCC4; its C-terminal region (aa 620–800) containing an NLS, BRCT I domain, and XRCC4-interacting region is essential for XRCC4 nuclear accumulation; Ligase IV also regulates XRCC4 protein stability. Expression of LigIV deletion constructs; subcellular fractionation/imaging; LigIV-deficient cell lines; Western blot for protein levels DNA repair Medium 24984242
2015 PAXX (paralog of XRCC4 and XLF) interacts directly with Ku and promotes Ku-dependent DNA ligation and assembly of core NHEJ factors; PAXX crystal structure resembles XRCC4; combined PAXX/XLF loss impairs DSB repair additively. Crystal structure; co-immunoprecipitation; CRISPR-Cas9 and RNAi knockouts; in vitro ligation assay; chromatin fractionation Science High 25574025
2016 FBXW7 (SCF E3 ligase) promotes K63-linked polyubiquitylation of XRCC4 at lysine 296 after DNA-PKcs phosphorylates XRCC4 at serines 325/326; this ubiquitylation enhances XRCC4 association with Ku70/80 to facilitate NHEJ; a small-molecule inhibitor blocking this ubiquitylation reduces NHEJ. In vivo ubiquitylation assay; site-directed mutagenesis; co-immunoprecipitation; NHEJ reporter assay; IR sensitivity assay; kinase assay Molecular cell High 26774286
2016 XRCC4-XLF complexes form mobile 'sliding sleeve' structures around DNA that can bridge two independent DNA molecules and diffuse along DNA; XLF stimulates XRCC4 binding to DNA; XRCC4-XLF bridges can slide along DNA, enabling rapid reconnection of broken ends. Dual- and quadruple-trap optical tweezers combined with fluorescence microscopy; single-molecule real-time imaging Nature High 27437582
2016 APLF is an intrinsically disordered protein that links Ku, DNA-PKcs, XRCC4-LigIV into an extended flexible NHEJ core complex via simultaneous interactions with Ku, DNA-PK, and X4L4; Ku80 C-terminal region connects DNA-PKcs to the X4L4 complex. SAXS; mutational analysis; in vitro complex reconstitution The Journal of biological chemistry Medium 27875301
2017 The PNKP-XRCC4-LigIV ternary complex requires CK2-phosphorylation of XRCC4 for stable PNKP binding; only one PNKP protomer binds per XRCC4 dimer; SAXS and HDX reveal multipoint contacts between PNKP and XRCC4-LigIV including a PNKP phosphatase surface (E326K disease mutation impairs PNKP recruitment to damaged DNA). Recombinant complex purification; SAXS; hydrogen-deuterium exchange; CK2 phosphorylation assay; site-directed mutagenesis; cellular recruitment assay Nucleic acids research High 28453785
2017 XRCC4-LigIV (X4-LIV) stimulates Artemis nuclease activity at 3' overhangs independently of DNA-PKcs; X4-LIV cannot stimulate Artemis at hairpins or 5' overhangs; X4-LIV and DNA-PKcs interfere with each other in stimulating Artemis, suggesting sequential not concurrent recruitment. In vitro nuclease assay with purified proteins; in vitro ligation assay; defined DNA substrates The Journal of biological chemistry High 28696258
2017 Phospho-mimicking mutations in the C-terminal tails of both XRCC4 and XLF (14 DNA-PK/ATM sites mutated to aspartate) destabilize XRCC4/XLF complexes and reduce DNA bridging activity without affecting LigIV stimulation, suggesting phosphorylation regulates DNA bridging independently of ligation. Phospho-blocking and -mimicking mutagenesis; DNA bridging assay; LigIV stimulation assay; complex stability analysis eLife High 28500754
2021 RIG-I interacts with XRCC4 and impedes formation of the XRCC4/LIG4/XLF complex at DSBs, suppressing NHEJ; reciprocally, XRCC4 promotes RIG-I signaling by enhancing RIG-I oligomerization and ubiquitination, augmenting type I IFN production. Co-immunoprecipitation; DSB repair assays; RIG-I/XRCC4 knockdown/overexpression; innate immune signaling assays; in vivo viral infection model Nature communications Medium 33846346

Source papers

Stage 0 corpus · 100 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2006 XLF interacts with the XRCC4-DNA ligase IV complex to promote DNA nonhomologous end-joining. Cell 596 16439205
1997 Activity of DNA ligase IV stimulated by complex formation with XRCC4 protein in mammalian cells. Nature 521 9242410
2000 Interplay of p53 and DNA-repair protein XRCC4 in tumorigenesis, genomic stability and development. Nature 482 10786799
1997 Mammalian DNA double-strand break repair protein XRCC4 interacts with DNA ligase IV. Current biology : CB 373 9259561
1995 The XRCC4 gene encodes a novel protein involved in DNA double-strand break repair and V(D)J recombination. Cell 371 8548796
2006 Dynamic assembly of end-joining complexes requires interaction between Ku70/80 and XRCC4. Proceedings of the National Academy of Sciences of the United States of America 322 17124166
2000 Ku recruits the XRCC4-ligase IV complex to DNA ends. Molecular and cellular biology 298 10757784
2015 DNA repair. PAXX, a paralog of XRCC4 and XLF, interacts with Ku to promote DNA double-strand break repair. Science (New York, N.Y.) 248 25574025
2001 Crystal structure of an Xrcc4-DNA ligase IV complex. Nature structural biology 204 11702069
1998 Double-strand break repair in Ku86- and XRCC4-deficient cells. Nucleic acids research 194 9826756
2004 Xrcc4 physically links DNA end processing by polynucleotide kinase to DNA ligation by DNA ligase IV. The EMBO journal 189 15385968
2000 Interactions of the DNA ligase IV-XRCC4 complex with DNA ends and the DNA-dependent protein kinase. The Journal of biological chemistry 175 10854421
2004 The ataxia-oculomotor apraxia 1 gene product has a role distinct from ATM and interacts with the DNA strand break repair proteins XRCC1 and XRCC4. DNA repair 164 15380105
1998 The XRCC4 gene product is a target for and interacts with the DNA-dependent protein kinase. The Journal of biological chemistry 153 9430729
1999 DNA binding of Xrcc4 protein is associated with V(D)J recombination but not with stimulation of DNA ligase IV activity. The EMBO journal 148 10202163
2000 Crystal structure of the Xrcc4 DNA repair protein and implications for end joining. The EMBO journal 147 11080143
1999 Absence of DNA ligase IV protein in XR-1 cells: evidence for stabilization by XRCC4. Mutation research 145 10047779
2007 Defects in XRCC4 and KU80 differentially affect the joining of distal nonhomologous ends. Proceedings of the National Academy of Sciences of the United States of America 139 18093953
2011 XRCC4 protein interactions with XRCC4-like factor (XLF) create an extended grooved scaffold for DNA ligation and double strand break repair. The Journal of biological chemistry 137 21775435
1998 Saccharomyces cerevisiae LIF1: a function involved in DNA double-strand break repair related to mammalian XRCC4. The EMBO journal 136 9670033
2007 XRCC4:DNA ligase IV can ligate incompatible DNA ends and can ligate across gaps. The EMBO journal 134 17290226
1998 Requirement for an interaction of XRCC4 with DNA ligase IV for wild-type V(D)J recombination and DNA double-strand break repair in vivo. The Journal of biological chemistry 132 9733770
2016 Sliding sleeves of XRCC4-XLF bridge DNA and connect fragments of broken DNA. Nature 128 27437582
2012 A human XRCC4-XLF complex bridges DNA. Nucleic acids research 121 22287571
2007 Role for DNA repair factor XRCC4 in immunoglobulin class switch recombination. The Journal of experimental medicine 119 17606631
2004 DNA-dependent protein kinase and XRCC4-DNA ligase IV mobilization in the cell in response to DNA double strand breaks. The Journal of biological chemistry 119 15520013
2016 FBXW7 Facilitates Nonhomologous End-Joining via K63-Linked Polyubiquitylation of XRCC4. Molecular cell 118 26774286
2009 Structural and functional interaction between the human DNA repair proteins DNA ligase IV and XRCC4. Molecular and cellular biology 116 19332554
1998 DNA ligase IV binds to XRCC4 via a motif located between rather than within its BRCT domains. Current biology : CB 115 9705934
2002 An xrcc4 defect or Wortmannin stimulates homologous recombination specifically induced by double-strand breaks in mammalian cells. Nucleic acids research 110 12140331
2011 Structural characterization of filaments formed by human Xrcc4-Cernunnos/XLF complex involved in nonhomologous DNA end-joining. Proceedings of the National Academy of Sciences of the United States of America 109 21768349
2007 Interaction of the Ku heterodimer with the DNA ligase IV/Xrcc4 complex and its regulation by DNA-PK. DNA repair 104 17241822
2003 DNA-PK phosphorylation sites in XRCC4 are not required for survival after radiation or for V(D)J recombination. DNA repair 104 14599745
2007 Single-stranded DNA ligation and XLF-stimulated incompatible DNA end ligation by the XRCC4-DNA ligase IV complex: influence of terminal DNA sequence. Nucleic acids research 100 17717001
2010 XLF regulates filament architecture of the XRCC4·ligase IV complex. Structure (London, England : 1993) 98 21070942
2006 Cernunnos interacts with the XRCC4 x DNA-ligase IV complex and is homologous to the yeast nonhomologous end-joining factor Nej1. The Journal of biological chemistry 97 16571728
2006 XRCC4 suppresses medulloblastomas with recurrent translocations in p53-deficient mice. Proceedings of the National Academy of Sciences of the United States of America 96 16670198
2007 Crystal structure of human XLF/Cernunnos reveals unexpected differences from XRCC4 with implications for NHEJ. The EMBO journal 95 18046455
2008 XLF-Cernunnos promotes DNA ligase IV-XRCC4 re-adenylation following ligation. Nucleic acids research 94 19056826
2003 Coordinated assembly of Ku and p460 subunits of the DNA-dependent protein kinase on DNA ends is necessary for XRCC4-ligase IV recruitment. Journal of molecular biology 93 12547193
2013 XRCC4 and XLF form long helical protein filaments suitable for DNA end protection and alignment to facilitate DNA double strand break repair. Biochemistry and cell biology = Biochimie et biologie cellulaire 90 23442139
2002 Defining interactions between DNA-PK and ligase IV/XRCC4. DNA repair 89 12509254
2007 Length-dependent binding of human XLF to DNA and stimulation of XRCC4.DNA ligase IV activity. The Journal of biological chemistry 88 17317666
2006 SUMO modification of human XRCC4 regulates its localization and function in DNA double-strand break repair. Molecular and cellular biology 82 16478998
2004 DNA polymerase lambda can elongate on DNA substrates mimicking non-homologous end joining and interact with XRCC4-ligase IV complex. Biochemical and biophysical research communications 80 15451442
2016 Specific Roles of XRCC4 Paralogs PAXX and XLF during V(D)J Recombination. Cell reports 73 27601299
2000 DNA ligase IV and XRCC4 form a stable mixed tetramer that functions synergistically with other repair factors in a cell-free end-joining system. The Journal of biological chemistry 69 10945980
2015 Mutations in the NHEJ component XRCC4 cause primordial dwarfism. American journal of human genetics 67 25728776
2004 End-joining of blunt DNA double-strand breaks in mammalian fibroblasts is precise and requires DNA-PK and XRCC4. DNA repair 64 14697758
2008 Distinct roles of XRCC4 and Ku80 in non-homologous end-joining of endonuclease- and ionizing radiation-induced DNA double-strand breaks. Nucleic acids research 62 18332040
2016 An Intrinsically Disordered APLF Links Ku, DNA-PKcs, and XRCC4-DNA Ligase IV in an Extended Flexible Non-homologous End Joining Complex. The Journal of biological chemistry 61 27875301
2008 Live cell imaging of XLF and XRCC4 reveals a novel view of protein assembly in the non-homologous end-joining pathway. Cell cycle (Georgetown, Tex.) 61 18418068
2008 Oncogenic transformation in the absence of Xrcc4 targets peripheral B cells that have undergone editing and switching. The Journal of experimental medicine 58 19064702
2003 Tetramerization and DNA ligase IV interaction of the DNA double-strand break repair protein XRCC4 are mutually exclusive. Journal of molecular biology 58 14607114
2011 Non-homologous end-joining partners in a helical dance: structural studies of XLF-XRCC4 interactions. Biochemical Society transactions 57 21936820
2019 Amyotrophic lateral sclerosis-associated TDP-43 mutation Q331K prevents nuclear translocation of XRCC4-DNA ligase 4 complex and is linked to genome damage-mediated neuronal apoptosis. Human molecular genetics 56 31067307
2012 XRCC4's interaction with XLF is required for coding (but not signal) end joining. Nucleic acids research 55 22228831
2008 Polymorphisms of LIG4 and XRCC4 involved in the NHEJ pathway interact to modify risk of glioma. Human mutation 55 18165945
2008 Werner protein cooperates with the XRCC4-DNA ligase IV complex in end-processing. Biochemistry 55 18558713
2006 Structure of an Xrcc4-DNA ligase IV yeast ortholog complex reveals a novel BRCT interaction mode. DNA repair 53 16388993
2004 Identification of DNA-PKcs phosphorylation sites in XRCC4 and effects of mutations at these sites on DNA end joining in a cell-free system. DNA repair 53 15177042
2000 Cleavage and phosphorylation of XRCC4 protein induced by X-irradiation. FEBS letters 53 10922471
2015 XRCC4/XLF Interaction Is Variably Required for DNA Repair and Is Not Required for Ligase IV Stimulation. Molecular and cellular biology 52 26100018
2010 Dual modes of interaction between XRCC4 and polynucleotide kinase/phosphatase: implications for nonhomologous end joining. The Journal of biological chemistry 52 20852255
2007 Variation in DNA repair genes XRCC3, XRCC4, XRCC5 and susceptibility to myeloma. Human molecular genetics 52 17901044
2015 An XRCC4 splice mutation associated with severe short stature, gonadal failure, and early-onset metabolic syndrome. The Journal of clinical endocrinology and metabolism 51 25742519
2007 Knockdown of DNA ligase IV/XRCC4 by RNA interference inhibits herpes simplex virus type I DNA replication. The Journal of biological chemistry 48 17296606
2021 Reciprocal regulation of RIG-I and XRCC4 connects DNA repair with RIG-I immune signaling. Nature communications 47 33846346
2017 Structural and functional characterization of the PNKP-XRCC4-LigIV DNA repair complex. Nucleic acids research 47 28453785
2013 Genetic polymorphisms in DNA repair genes XRCC4 and XRCC5 and aflatoxin B1-related hepatocellular carcinoma. Epidemiology (Cambridge, Mass.) 45 23788213
2007 Modes of interaction among yeast Nej1, Lif1 and Dnl4 proteins and comparison to human XLF, XRCC4 and Lig4. DNA repair 44 17567543
2015 XRCC4 deficiency in human subjects causes a marked neurological phenotype but no overt immunodeficiency. The Journal of allergy and clinical immunology 43 26255102
2010 Delineation of the Xrcc4-interacting region in the globular head domain of cernunnos/XLF. The Journal of biological chemistry 41 20558749
2008 Association of XRCC4 codon 247 polymorphism with oral cancer susceptibility in Taiwan. Anticancer research 40 18630527
2007 Processing of DNA for nonhomologous end-joining is controlled by kinase activity and XRCC4/ligase IV. The Journal of biological chemistry 40 17272270
2015 ZNF281 contributes to the DNA damage response by controlling the expression of XRCC2 and XRCC4. Oncogene 39 26300006
1997 Molecular genetic characterization of XRCC4 function. International immunology 38 9352367
2003 Requirement for XRCC4 and DNA ligase IV in alignment-based gap filling for nonhomologous DNA end joining in vitro. Cancer research 37 12517771
2002 Identification of human autoantibodies to the DNA ligase IV/XRCC4 complex and mapping of an autoimmune epitope to a potential regulatory region. Journal of immunology (Baltimore, Md. : 1950) 37 12218164
2007 Human DNA ligase IV and the ligase IV/XRCC4 complex: analysis of nick ligation fidelity. Biochemistry 36 17407264
2017 Mutational phospho-mimicry reveals a regulatory role for the XRCC4 and XLF C-terminal tails in modulating DNA bridging during classical non-homologous end joining. eLife 35 28500754
2010 Colorectal cancer and genetic polymorphism of DNA double-strand break repair gene XRCC4 in Taiwan. Anticancer research 35 20683005
2018 Role of PON1, SOD2, OGG1, XRCC1, and XRCC4 polymorphisms on modulation of DNA damage in workers occupationally exposed to pesticides. Ecotoxicology and environmental safety 34 29747151
2015 The TMPRSS2-ERG Gene Fusion Blocks XRCC4-Mediated Nonhomologous End-Joining Repair and Radiosensitizes Prostate Cancer Cells to PARP Inhibition. Molecular cancer therapeutics 34 26026052
2011 Gene variants of XRCC4 and XRCC3 and their association with risk for urothelial bladder cancer. Molecular biology reports 34 21617942
2008 Efficiency of the DNA repair and polymorphisms of the XRCC1, XRCC3 and XRCC4 DNA repair genes in systemic lupus erythematosus. Lupus 33 18852222
2017 Effects of DNA end configuration on XRCC4-DNA ligase IV and its stimulation of Artemis activity. The Journal of biological chemistry 30 28696258
2015 A systematic gene-gene and gene-environment interaction analysis of DNA repair genes XRCC1, XRCC2, XRCC3, XRCC4, and oral cancer risk. Omics : a journal of integrative biology 30 25831063
2015 Mutations in XRCC4 cause primary microcephaly, short stature and increased genomic instability. Human molecular genetics 30 25839420
2018 UHRF1 depletion sensitizes retinoblastoma cells to chemotherapeutic drugs via downregulation of XRCC4. Cell death & disease 29 29415984
2010 Genetic polymorphisms in DNA repair genes XPC, XPD, and XRCC4, and susceptibility to Helicobacter pylori infection-related gastric antrum adenocarcinoma in Guangxi population, China. Molecular carcinogenesis 27 20232359
2019 Genetic interaction between DNA repair factors PAXX, XLF, XRCC4 and DNA-PKcs in human cells. FEBS open bio 25 31141305
2014 DNA Ligase IV regulates XRCC4 nuclear localization. DNA repair 25 24984242
2009 Electron microscopy of Xrcc4 and the DNA ligase IV-Xrcc4 DNA repair complex. DNA repair 24 19837014
2015 Versatility in phospho-dependent molecular recognition of the XRCC1 and XRCC4 DNA-damage scaffolds by aprataxin-family FHA domains. DNA repair 23 26519825
2011 XRCC4 controls nuclear import and distribution of Ligase IV and exchanges faster at damaged DNA in complex with Ligase IV. DNA repair 23 21982441
2009 Lung cancer susceptibility and genetic polymorphism of DNA repair gene XRCC4 in Taiwan. Cancer biomarkers : section A of Disease markers 23 19729825
2019 Silencing of XRCC4 increases radiosensitivity of triple-negative breast cancer cells. Bioscience reports 22 30842344
2018 Normal development of mice lacking PAXX, the paralogue of XRCC4 and XLF. FEBS open bio 22 29511619
2010 Radiation-induced XRCC4 association with chromatin DNA analyzed by biochemical fractionation. Journal of radiation research 22 20448413

Missed literature

Know a paper Affinage missed for XRCC4? Flag it for the maintainers and the community.

No submissions yet.