ATP Dependent DNA ligase IV (LIG4)

LIG4 is an ATP-dependent DNA ligase that joins double-strand breaks during the non-homologous end joining pathway of double-strand break repair. It is also essential for V(D)J recombination. Lig4 forms a complex with XRCC4, and further interacts with the DNA-dependent protein kinase (DNA-PK) and XLF/Cernunnos, which are also required for NHEJ. The crystal structure of the Lig4/XRCC4 complex has been resolved.

Efficiently joins single-strand breaks in a double-stranded polydeoxynucleotide in an ATP-dependent reaction. Involved in DNA non-homologous end joining (NHEJ) required for double-strand break repair and V(D)J recombination. The LIG4-XRCC4 complex is responsible for the NHEJ ligation step, and XRCC4 enhances the joining activity of LIG4.