DNA repair protein XRCC4; X-ray repair cross-complementing protein 4 (XRCC4)

Function

• role in DNA non-homologous end joining (NHEJ) required for double-strand break repair & V(D)J recombination
• binds to DNA & to DNA ligase IV (LIG4)
• the LIG4-XRCC4 complex is responsible for the NHEJ ligation step, & XRCC4 enhances the joining activity of LIG4
• binding of the LIG4-XRCC4 complex to DNA ends is dependent on the assembly of the DNA-dependent protein kinase complex DNA-PK to these DNA ends
• phosphorylated by PRKDC; phosphorylation seems not to be necessary for binding to DNA
• phosphorylation by CK2 promotes interaction with APTX
• monoubiquitinated
• sumoylation at Lys-210 is required for nuclear localization & recombination efficiency; has no effect on ubiquitination
• homodimer & homotetramer in solution
• homodimer associates with LIG4, & the LIG4-XRCC4 complex associates in a DNA-dependent manner with the DNA-PK complex formed by the Ku p70/p86 dimer (G22P1/G22P2) & PRKDC
• seems to interact directly with PRKDC but not with the Ku p70/86 dimer
• interacts with XLF/cernunnos
• interacts with APTX & APLF

Structure

belongs to the XRCC4 family

Compartment

nucleus

Alternative splicing

named isoforms=3

Expression

widely expressed

More general terms

• nuclear protein
• phosphoprotein

Database

• Entrez gene: http://www.ncbi.nlm.nih.gov/sites/entrez?db=gene&cmd=Retrieve&dopt=Graphics&list_uids=7518
• Kegg: http://www.genome.jp/dbget-bin/www_bget?hsa:7518
• OMIM: https://mirror.omim.org/entry/194363
• UniProt: http://www.uniprot.org/uniprot/Q13426.html