NHEJ1

Double-strand breaks in DNA result from genotoxic stresses and are among the most damaging of DNA lesions. This gene encodes a DNA repair factor essential for the nonhomologous end-joining pathway, which preferentially mediates repair of double-stranded breaks. Mutations in this gene cause different kinds of severe combined immunodeficiency disorders.

Non-Homologous End Joining Factor 1

DNA repair protein involved in DNA non-homologous end joining (NHEJ); required for double-strand break (DSB) repair and V(D)J recombination (PubMed:16439204, PubMed:16439205, PubMed:17717001, PubMed:17317666, PubMed:17470781, PubMed:18644470, PubMed:20558749, PubMed:26100018, PubMed:18158905).
Plays a key role in NHEJ by promoting the ligation of various mismatched and non-cohesive ends (PubMed:17717001, PubMed:17470781, PubMed:19056826).
Together with PAXX, collaborates with DNA polymerase lambda (POLL) to promote joining of non-cohesive DNA ends (PubMed:30250067, PubMed:25670504).
May act in concert with XRCC5-XRCC6 (Ku) to stimulate XRCC4-mediated joining of blunt ends and several types of mismatched ends that are non-complementary or partially complementary (PubMed:16439204, PubMed:16439205, PubMed:17317666, PubMed:17470781).
Associates with XRCC4 to form alternating helical filaments that bridge DNA and act like a bandage, holding together the broken DNA until it is repaired (PubMed:22228831, PubMed:26100018, PubMed:28500754, PubMed:27437582, PubMed:21775435, PubMed:22287571, PubMed:21768349).
The XRCC4-NHEJ1/XLF subcomplex binds to the DNA fragments of a DSB in a highly diffusive manner and robustly bridges two independent DNA molecules, holding the broken DNA fragments in close proximity to one other (PubMed:28500754, PubMed:27437582).
The mobility of the bridges ensures that the ends remain accessible for further processing by other repair factors (PubMed:27437582).
Binds DNA in a length-dependent manner (PubMed:17317666, PubMed:18158905).

B cell differentiationManual Assertion Based On ExperimentIMP:UniProtKB
Central nervous system development1 PublicationNAS:UniProtKB
DNA ligation involved in DNA repairManual Assertion Based On ExperimentIDA:UniProtKB
Double-strand break repair via nonhomologous end joiningManual Assertion Based On ExperimentIDA:UniProtKB
Immunoglobulin V(D)J recombinationManual Assertion Based On ExperimentIDA:UniProtKB
Positive regulation of ligase activity1 PublicationNAS:UniProtKB
Response to ionizing radiationManual Assertion Based On ExperimentIDA:UniProtKB
T cell differentiationManual Assertion Based On ExperimentIMP:UniProtKB

Nucleus
Chromosome
Localizes to site of double-strand breaks; recruitment is dependent on XRCC5-XRCC6 (Ku) heterodimer.

Severe combined immunodeficiency due to NHEJ1 deficiency (NHEJ1-SCID):
SCID refers to a genetically and clinically heterogeneous group of rare congenital disorders characterized by impairment of both humoral and cell-mediated immunity, leukopenia and low or absent antibody levels. Patients with SCID present in infancy with recurrent, persistent infections by opportunistic organisms. The common characteristic of all types of SCID is absence of T-cell-mediated cellular immunity due to a defect in T-cell development. NHEJ1-SCID is characterized by a profound T- and B-lymphocytopenia associated with increased cellular sensitivity to ionizing radiation, microcephaly and growth retardation. Some patients may manifest SCID with sensitivity to ionizing radiation without microcephaly and mild growth retardation, probably due to hypomorphic NHEJ1 mutations.

Phosphorylated by PRKDC at the C-terminus in response to DNA damage (PubMed:18644470, PubMed:22228831, PubMed:28500754).
Phosphorylations by PRKDC at the C-terminus of XRCC4 and NHEJ1/XLF are highly redundant and regulate ability of the XRCC4-NHEJ1/XLF subcomplex to bridge DNA (PubMed:22228831, PubMed:28500754).
Phosphorylation does not prevent interaction with XRCC4 but disrupts ability to bridge DNA and promotes detachment from DNA (PubMed:22228831, PubMed:28500754).