DNA polymerase mu

DNA polymerase mu is a polymerase enzyme found in eukaryotes. In humans, this protein is encoded by the POLM gene.^[5]

POLM
Available structures PDB Ortholog search: PDBe RCSB List of PDB id codes 2HTF, 4LZD, 4M04, 4M0A, 4YCX, 4YD1, 4YD2, 2DUN
Identifiers
Aliases	POLM, Pol Mu, Tdt-N, DNA polymerase mu, polymerase (DNA) mu
External IDs	OMIM: 606344; MGI: 1860191; HomoloGene: 41170; GeneCards: POLM; OMA:POLM - orthologs
Gene location (Human) Chr. Chromosome 7 (human)[1] Band 7p13 Start 44,072,062 bp[1] End 44,082,530 bp[1]
Gene location (Mouse) Chr. Chromosome 11 (mouse)[2] Band 11|11 A1 Start 5,777,860 bp[2] End 5,788,016 bp[2]
RNA expression pattern Bgee Human Mouse (ortholog) Top expressed in granulocyte right lobe of thyroid gland spleen left lobe of thyroid gland blood right uterine tube right lobe of liver lymph node fundus gastric mucosa Top expressed in zygote Ileal epithelium secondary oocyte granulocyte perirhinal cortex lactiferous gland entorhinal cortex primary oocyte lip choroid plexus of fourth ventricle More reference expression data BioGPS More reference expression data
Gene ontology Molecular function transferase activity DNA binding DNA-directed DNA polymerase activity nucleotidyltransferase activity protein binding metal ion binding DNA polymerase DNA polymerase activity Cellular component nucleus nucleoplasm Biological process somatic hypermutation of immunoglobulin genes B cell differentiation DNA recombination double-strand break repair via nonhomologous end joining cellular response to DNA damage stimulus DNA repair DNA biosynthetic process Sources:Amigo / QuickGO
Orthologs Species Human Mouse Entrez 27434 54125 Ensembl ENSG00000122678 ENSMUSG00000020474 UniProt Q9NP87 Q9JIW4 RefSeq (mRNA) NM_001284330 NM_001284331 NM_013284 NM_001362683 NM_017401 RefSeq (protein) NP_001271259 NP_001271260 NP_037416 NP_001349612 NP_059097 Location (UCSC) Chr 7: 44.07 – 44.08 Mb Chr 11: 5.78 – 5.79 Mb PubMed search [3] [4]
Wikidata
View/Edit Human View/Edit Mouse

Function

Pol μ is a member of the X family of DNA polymerases. It participates in resynthesis of damaged or missing nucleotides during the non-homologous end joining (NHEJ) pathway of DNA repair.^[6] Pol μ interacts with Ku and DNA ligase IV, which also participate in NHEJ.^[7] It is structurally and functionally related to pol λ, and, like pol λ, pol μ has a BRCT domain that is thought to mediate interactions with other DNA repair proteins.^[8] Unlike pol λ, however, pol μ has the unique ability to add a base to a blunt end that is templated by the overhang on the opposite end of the double-strand break.^[9] Pol μ is also closely related to terminal deoxynucleotidyl transferase (TdT), a specialized DNA polymerase that adds random nucleotides to DNA ends during V(D)J recombination, the process by which B-cell and T-cell receptor diversity is generated in the vertebrate immune system. Like TdT, pol μ participates in V(D)J recombination, but only during light chain rearrangements.^[10] This is distinct from pol λ, which is involved in heavy chain rearrangements.^[11]

POLM mutant mice

In polymerase mu mutant mice, hematopoietic cell development is defective in several peripheral and bone marrow cell populations with about a 40% decrease in bone marrow cell number that includes several hematopoietic lineages.^[12] Expansion potential of hematopoietic progenitor cells is also reduced. These characteristics correlate with reduced ability to repair double-strand breaks in hematopoietic tissue. Whole body gamma irradiation of polymerase mu mutant mice indicates that polymerase mu also has a role in double-strand break repair in other tissues unrelated to hematopoietic tissue. Thus polymerase mu has a significant role in maintaining genetic stability in hematopoietic and non-hematopoietic tissue.

References

1. GRCh38: Ensembl release 89: ENSG00000122678 – Ensembl, May 2017
2. GRCm38: Ensembl release 89: ENSMUSG00000020474 – Ensembl, May 2017
3. "Human PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
4. "Mouse PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
5. "Entrez Gene: POLM polymerase (DNA directed), mu".
6. Daley JM, Laan RL, Suresh A, Wilson TE (August 2005). "DNA joint dependence of pol X family polymerase action in nonhomologous end joining". J. Biol. Chem. 280 (32): 29030–7. doi:10.1074/jbc.M505277200. PMID 15964833.
7. Mahajan KN, Nick McElhinny SA, Mitchell BS, Ramsden DA (July 2002). "Association of DNA polymerase mu (pol mu) with Ku and ligase IV: role for pol mu in end-joining double-strand break repair". Mol. Cell. Biol. 22 (14): 5194–202. doi:10.1128/MCB.22.14.5194-5202.2002. PMC 139779. PMID 12077346.
8. Nick McElhinny SA, Ramsden DA (August 2004). "Sibling rivalry: competition between Pol X family members in V(D)J recombination and general double strand break repair". Immunol. Rev. 200: 156–64. doi:10.1111/j.0105-2896.2004.00160.x. PMID 15242403. S2CID 36516952.
9. Nick McElhinny SA, Havener JM, Garcia-Diaz M, et al. (August 2005). "A gradient of template dependence defines distinct biological roles for family X polymerases in nonhomologous end joining". Mol. Cell. 19 (3): 357–66. doi:10.1016/j.molcel.2005.06.012. PMID 16061182.
10. Bertocci B, De Smet A, Berek C, Weill JC, Reynaud CA (August 2003). "Immunoglobulin kappa light chain gene rearrangement is impaired in mice deficient for DNA polymerase mu". Immunity. 19 (2): 203–11. doi:10.1016/S1074-7613(03)00203-6. PMID 12932354.
11. Bertocci B, De Smet A, Weill JC, Reynaud CA (July 2006). "Nonoverlapping functions of DNA polymerases mu, lambda, and terminal deoxynucleotidyltransferase during immunoglobulin V(D)J recombination in vivo" (PDF). Immunity. 25 (1): 31–41. doi:10.1016/j.immuni.2006.04.013. PMID 16860755.
12. Lucas D, Escudero B, Ligos JM, Segovia JC, Estrada JC, Terrados G, Blanco L, Samper E, Bernad A (Feb 2009). "Altered hematopoiesis in mice lacking DNA polymerase mu is due to inefficient double-strand break repair". PLOS Genet. 5 (2): e1000389. doi:10.1371/journal.pgen.1000389. PMC 2638008. PMID 19229323.

External links

• Overview of all the structural information available in the PDB for UniProt: Q9NP87 (Human DNA-directed DNA/RNA polymerase mu) at the PDBe-KB.