DNA ligase-4 (LIG4)

Function

• efficiently joins single-strand breaks in a double-stranded polydeoxynucleotide (ATP-dependent)
• role in DNA nonhomologous end joining (NHEJ) required for double-strand break repair & V(D)J recombination
• binds to XRCC4
• the LIG4-XRCC4 complex has probably a 1:2 stoichiometry
• 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
• the LIG4-XRCC4 heteromer associates in a DNA-dependent manner with the DNA-dependent protein kinase complex DNA-PK, formed by the Ku p70/p86 dimer (G22P1/G22P2) & PRKDC

ATP + (deoxyribonucleotide)(n) + (deoxyribonucleotide)(m)
                    <-->
AMP + diphosphate + (deoxyribonucleotide)(n+m)

Structure

• belongs to the ATP-dependent DNA ligase family
• contains 2 BRCT domains

Compartment

nucleus

Expression

testis, thymus, prostate & heart

Pathology

• defects in LIG4 are the cause of LIG4 syndrome

More general terms

• ATP-dependent DNA ligase
• phosphoprotein

Database

• UniProt: http://www.uniprot.org/uniprot/P49917.html
• Kegg: http://www.genome.jp/dbget-bin/www_bget?hsa:3981
• OMIM: https://mirror.omim.org/entry/601837
• OMIM: https://mirror.omim.org/entry/606593