Contents

DNA ligase 4

Enzyme found in humans

LIG4
Available structures PDB Ortholog search: PDBe RCSB List of PDB id codes 1IK9, 2E2W, 3II6, 3VNN, 3W1B, 3W1G, 3W5O, 4HTO, 4HTP
Identifiers
Aliases	LIG4, LIG4S, DNA ligase 4
External IDs	OMIM: 601837; MGI: 1335098; HomoloGene: 1736; GeneCards: LIG4; OMA:LIG4 - orthologs
Gene location (Human) Chr. Chromosome 13 (human)[1] Band 13q33.3 Start 108,207,439 bp[1] End 108,218,368 bp[1]
Gene location (Mouse) Chr. Chromosome 8 (mouse)[2] Band 8|8 A1.1 Start 10,019,049 bp[2] End 10,027,686 bp[2]
RNA expression pattern Bgee Human Mouse (ortholog) Top expressed in endothelial cell oocyte secondary oocyte mucosa of paranasal sinus retinal pigment epithelium Brodmann area 23 islet of Langerhans jejunal mucosa primary visual cortex lower lobe of lung Top expressed in primary oocyte secondary oocyte thymus zygote hand trigeminal ganglion otolith organ epithelium of lens utricle substantia nigra More reference expression data BioGPS More reference expression data
Gene ontology Molecular function nucleotide binding metal ion binding protein C-terminus binding protein binding ATP binding DNA ligase (ATP) activity ligase activity DNA binding DNA ligase activity Cellular component nucleoplasm DNA ligase IV complex nonhomologous end joining complex condensed chromosome nucleus DNA-dependent protein kinase-DNA ligase 4 complex cytoplasm cytoplasmic ribonucleoprotein granule Biological process nucleotide-excision repair, DNA gap filling double-strand break repair via classical nonhomologous end joining response to ionizing radiation DNA recombination lagging strand elongation DNA biosynthetic process cellular response to lithium ion single strand break repair cellular response to DNA damage stimulus cell division DNA replication positive regulation of chromosome organization establishment of integrated proviral latency cell cycle response to X-ray positive regulation of neurogenesis DNA ligation involved in DNA recombination DNA ligation DNA ligation involved in DNA repair somatic stem cell population maintenance chromosome organization T cell receptor V(D)J recombination neuron apoptotic process isotype switching T cell differentiation in thymus central nervous system development immunoglobulin V(D)J recombination double-strand break repair via nonhomologous end joining positive regulation of fibroblast proliferation in utero embryonic development cell population proliferation V(D)J recombination pro-B cell differentiation DNA repair response to gamma radiation double-strand break repair negative regulation of neuron apoptotic process cellular response to ionizing radiation Sources:Amigo / QuickGO
Orthologs Species Human Mouse Entrez 3981 319583 Ensembl ENSG00000174405 ENSMUSG00000049717 UniProt P49917 Q8BTF7 RefSeq (mRNA) NM_001098268 NM_002312 NM_206937 NM_001330595 NM_001352598 NM_001352599 NM_001352600 NM_001352601 NM_001352602 NM_001352603 NM_001352604 NM_001379095 NM_176953 NM_001377042 RefSeq (protein) NP_001091738 NP_001317524 NP_002303 NP_996820 NP_001339527 NP_001339528 NP_001339529 NP_001339530 NP_001339531 NP_001339532 NP_001339533 NP_001366024 NP_795927 NP_001363971 Location (UCSC) Chr 13: 108.21 – 108.22 Mb Chr 8: 10.02 – 10.03 Mb PubMed search [3] [4]
Wikidata
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DNA ligase 4 also DNA ligase IV, is an enzyme that in humans is encoded by the LIG4 gene.^[5]

DNA ligase 4 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.^[6] Defects in this gene are the cause of LIG4 syndrome. The yeast homolog of Lig4 is Dnl4.

In humans, deficiency of DNA ligase 4 results in a clinical condition known as LIG4 syndrome. This syndrome is characterized by cellular radiation sensitivity, growth retardation, developmental delay, microcephaly, facial dysmorphisms, increased disposition to leukemia, variable degrees of immunodeficiency and reduced number of blood cells.^[7][8]

Accumulation of DNA damage leading to stem cell exhaustion is regarded as an important aspect of aging.^[9][10] Deficiency of lig4 in pluripotent stem cells impairs Non-homologous end joining (NHEJ) and results in accumulation of DNA double-strand breaks and enhanced apoptosis.^[8] Lig4 deficiency in the mouse causes a progressive loss of haematopoietic stem cells and bone marrow cellularity during aging.^[11] The sensitivity of haematopoietic stem cells to lig4 deficiency suggests that lig4-mediated NHEJ is a key determinant of the ability of stem cells to maintain themselves against physiological stress over time.^[8][11]

LIG4 has been shown to interact with XRCC4 via its BRCT domain.^[12][6] This interaction stabilizes LIG4 protein in cells; cells that are deficient for XRCC4, such as XR-1 cells, have reduced levels of LIG4.^[13]

LIG4 is an ATP-dependent DNA ligase. LIG4 uses ATP to adenylate itself and then transfers the AMP group to the 5' phosphate of one DNA end. Nucleophilic attack by the 3' hydroxyl group of a second DNA end and release of AMP yield the ligation product. Adenylation of LIG4 is stimulated by XRCC4 and XLF.^[14]