DNA ligase 4 (LIG4) is involved in DNA double-strand break repair []. In higher eukaryotes it forms a complex with XRCC4, which is responsible for the ligation step during the DNA-PK-dependent non-homologous end joining (D-NHEJ) [, ]. The Ku component of the DNA-PK (DNA-dependent protein kinase) complex contributes to the recruitment of the LIG4-XRCC4 complex at the DNA break site [].
This entry represents the DNA ligase IV (Lig4) sequences between the two BRCA1 C-terminal (BRCT) domains. Lig4 along with Xrcc4 functions in DNA non-homologous end joining. This process is required to mend double-strand breaks. Upon ligase binding to an Xrcc4 dimer, the helical tails unwind leading to a flat interaction surface [].
This entry represents the DNA double-strand break repair and V(D)J recombination protein XRCC4, which is found in certain Metazoans, fungi and plants. XRCC4 binds to DNA, and to DNA ligase IV (LIG4) to form the LIG4-XRCC4 complex []. The LIG4-XRCC4 complex is responsible for the ligation step in the non-homologous end joining (NHEJ) pathway of DNA double-strand break repair. XRCC4 enhances the joining activity of LIG4. It is thought that XRCC4 and LIG4 are essential for alignment-based gap filling, as well as for final ligation of the breaks []. 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.
This is the N-terminal of the DNA repair protein Rad54 []. Rad54 functions in the recombinational DNA repair (RAD52) pathway. It dissociates RAD51 from nucleoprotein filaments formed on dsDNA and could be involved in the turnover of RAD51 protein-dsDNA filaments. Deficient mice also show significantly shorter telomeres than wild-type controls, indicating that the protein activity plays an essential role in telomere length maintenance in mammals. Non-homologous end joining (NHEJ) and homologous recombination (HR) represent the two major pathways of DNA double-strand break (DSB) repair in eukaryotic cells. LIG4 and RAD54L cooperate to support cellular proliferation, repair spontaneous DSBs, and prevent chromosome and single chromatid aberrations [, ].
