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N-terminal head domain found in XRCC4-like factor and similar proteins XRCC4-like factor (XLF), also known as non-homologous end-joining factor 1 (NHEJ1) or protein cernunnos, is involved in DNA nonhomologous end joining (NHEJ), which is required for double-strand break (DSB) repair and V(D)J recombination. It interacts with the XRCC4-DNA ligase IV complex to promote NHEJ. It may act in concert with XRCC6/XRCC5 (Ku) to stimulate XRCC4-mediated joining of blunt ends and several types of mismatched ends that are non-complementary or partially complementary. XLF binds DNA in a length-dependent manner. Similar to XRCC4, XLF monomers are comprised of an N-terminal globular head domain, a centrally located coiled-coil, and a C-terminal region. These monomers homodimerize through two dimerization domains, the N-terminal globular head domains and long extended alpha-helical coiled-coil regions. In addition, XLF and XRCC4 form symmetric heterodimers that interact through their globular head domains at the opposite end of the homodimer interface, and may form XLF-XRCC4 filaments. This model corresponds to the N-terminal head domain of XLF, which is structurally related to other XRCC4-superfamily members, XRCC4, PAXX, SAS6, and CCDC61. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",