POLG

Last updated
POLG
Available structures
PDB Ortholog search: PDBe RCSB
Identifiers
Aliases POLG , MDP1, MIRAS, MTDPS4A, MTDPS4B, PEO, POLG1, POLGA, SANDO, SCAE, polymerase (DNA) gamma, catalytic subunit, DNA polymerase gamma, catalytic subunit, ORF-Y, POLGARF
External IDs OMIM: 174763 MGI: 1196389 HomoloGene: 2016 GeneCards: POLG
Orthologs
SpeciesHumanMouse
Entrez

5428

18975

Ensembl

ENSG00000140521

ENSMUSG00000039176

UniProt

P54098

P54099

RefSeq (mRNA)

NM_002693
NM_001126131

NM_017462
NM_001360095
NM_001360096

RefSeq (protein)

NP_001119603
NP_002684

n/a

Location (UCSC) Chr 15: 89.31 – 89.33 Mb Chr 7: 79.1 – 79.12 Mb
PubMed search [3] [4]
Wikidata
View/Edit Human View/Edit Mouse

DNA polymerase subunit gamma (POLG or POLG1) is an enzyme that in humans is encoded by the POLG gene. [5] Mitochondrial DNA polymerase is heterotrimeric, consisting of a homodimer of accessory subunits plus a catalytic subunit. The protein encoded by this gene is the catalytic subunit of mitochondrial DNA polymerase. Defects in this gene are a cause of progressive external ophthalmoplegia with mitochondrial DNA deletions 1 (PEOA1), sensory ataxic neuropathy dysarthria and ophthalmoparesis (SANDO), Alpers-Huttenlocher syndrome (AHS), and mitochondrial neurogastrointestinal encephalopathy syndrome (MNGIE). [6]

Contents

Structure

POLG is located on the q arm of chromosome 15 in position 26.1 and has 23 exons. The POLG gene produces a 140 kDa protein composed of 1239 amino acids. [7] [8] POLG, the protein encoded by this gene, is a member of the DNA polymerase type-A family. It is a mitochondrion nucleiod with an Mg2+ cofactor and 15 turns, 52 beta strands, and 39 alpha helixes. [9] [10] POLG contains a polyglutamine tract near its N-terminus that may be polymorphic. Two transcript variants encoding the same protein have been found for this gene. [6]

Function

POLG is a gene that codes for the catalytic subunit of the mitochondrial DNA polymerase, called DNA polymerase gamma. [6] The human POLG cDNA and gene were cloned and mapped to chromosome band 15q25. [11] In eukaryotic cells, the mitochondrial DNA is replicated by DNA polymerase gamma, a trimeric protein complex composed of a catalytic subunit, POLG, and a dimeric accessory subunit of 55 kDa encoded by the POLG2 gene. [12] The catalytic subunit contains three enzymatic activities, a DNA polymerase activity, a 3’-5’ exonuclease activity that proofreads misincorporated nucleotides, and a 5’-dRP lyase activity required for base excision repair.

Catalytic activity

Deoxynucleoside triphosphate + DNA(n) = diphosphate + DNA(n+1). [9] [10]

Clinical significance

Mutations in the POLG gene are associated with several mitochondrial diseases, progressive external ophthalmoplegia with mitochondrial DNA deletions 1 (PEOA1), sensory ataxic neuropathy dysarthria and ophthalmoparesis (SANDO), Alpers-Huttenlocher syndrome (AHS), and mitochondrial neurogastrointestinal encephalopathy syndrome (MNGIE). [6] Pathogenic variants have also been linked with fatal congenital myopathy and gastrointestinal pseudo-obstruction and fatal infantile hepatic failure. [13] [14] A list of all published mutations in the POLG coding region and their associated disease can be found at the Human DNA Polymerase Gamma Mutation Database.

Mice heterozygous for a Polg mutation are only able to replicate their mitochondrial DNA inaccurately, so that they sustain a 500-fold higher mutation burden than normal mice. These mice show no clear features of rapidly accelerated aging, indicating that mitochondrial mutations do not have a causal role in natural aging. [15]

Interactions

POLG has been shown to have 50 binary protein-protein interactions including 32 co-complex interactions. POLG appears to interact with POLG2, Dlg4, Tp53, and Sod2. [16]

Related Research Articles

<span class="mw-page-title-main">DNA polymerase</span> Form of DNA replication

A DNA polymerase is a member of a family of enzymes that catalyze the synthesis of DNA molecules from nucleoside triphosphates, the molecular precursors of DNA. These enzymes are essential for DNA replication and usually work in groups to create two identical DNA duplexes from a single original DNA duplex. During this process, DNA polymerase "reads" the existing DNA strands to create two new strands that match the existing ones. These enzymes catalyze the chemical reaction

<span class="mw-page-title-main">Human mitochondrial genetics</span> Study of the human mitochondrial genome

Human mitochondrial genetics is the study of the genetics of human mitochondrial DNA. The human mitochondrial genome is the entirety of hereditary information contained in human mitochondria. Mitochondria are small structures in cells that generate energy for the cell to use, and are hence referred to as the "powerhouses" of the cell.

T7 DNA helicase (gp4) is a hexameric motor protein encoded by T7 phages that uses energy from dTTP hydrolysis to process unidirectionally along single stranded DNA, separating (helicase) the two strands as it progresses. It is also a primase, making short stretches of RNA that initiates DNA synthesis. It forms a complex with T7 DNA polymerase. Its homologs are found in mitochondria and chloroplasts.

Chronic progressive external ophthalmoplegia (CPEO) is a type of eye disorder characterized by slowly progressive inability to move the eyes and eyebrows. It is often the only feature of mitochondrial disease, in which case the term CPEO may be given as the diagnosis. In other people suffering from mitochondrial disease, CPEO occurs as part of a syndrome involving more than one part of the body, such as Kearns–Sayre syndrome. Occasionally CPEO may be caused by conditions other than mitochondrial diseases.

<span class="mw-page-title-main">POLD1</span> Protein-coding gene in the species Homo sapiens

DNA polymerase delta catalytic subunit(DPOD1) is an enzyme that is encoded in the human by the POLD1 gene, in the DNA polymerase delta complex. DPOD1 is responsible for synthesizing the lagging strand of DNA, and has also been implicated in some activities at the leading strand. The DPOD1 subunit encodes both DNA polymerizing and exonuclease domains, which provide the protein an important second function in proofreading to ensure replication accuracy during DNA synthesis, and in a number of types of replication-linked DNA repair following DNA damage.

<span class="mw-page-title-main">Twinkle (protein)</span> Human mitochondrial protein

Twinkle protein also known as twinkle mtDNA helicase is a mitochondrial protein that in humans is encoded by the TWNK gene located in the long arm of chromosome 10 (10q24.31).

<span class="mw-page-title-main">RRM2B</span> Protein-coding gene in the species Homo sapiens

Ribonucleotide-diphosphate reductase subunit M2 B is an enzyme that in humans is encoded by the RRM2B gene. The gene encoding the RRM2B protein is located on chromosome 8, at position 8q23.1. The gene and its products are also known by designations MTDPS8A, MTDPS8B, and p53R2.

<span class="mw-page-title-main">POLG2</span> Protein-coding gene in the species Homo sapiens

DNA polymerase subunit gamma-2, mitochondrial is a protein that in humans is encoded by the POLG2 gene. The POLG2 gene encodes a 55 kDa accessory subunit protein that imparts high processivity and salt tolerance to the catalytic subunit of DNA polymerase gamma, encoded by the POLG gene. Mutations in this gene result in autosomal dominant progressive external ophthalmoplegia with mitochondrial DNA deletions.

<span class="mw-page-title-main">NDUFV1</span> Protein-coding gene in the species Homo sapiens

NADH dehydrogenase [ubiquinone] flavoprotein 1, mitochondrial (NDUFV1) is an enzyme that in humans is encoded by the NDUFV1 gene. The NDUFV1 gene encodes the 51-kD subunit of complex I of the mitochondrial respiratory chain. Defects in complex I are a common cause of mitochondrial dysfunction. Mitochondrial complex I deficiency is linked to myopathies, encephalomyopathies, and neurodegenerative disorders such as Parkinson's disease and Leigh syndrome.

<span class="mw-page-title-main">NDUFS8</span> Protein-coding gene in the species Homo sapiens

NADH dehydrogenase [ubiquinone] iron-sulfur protein 8, mitochondrial also known as NADH-ubiquinone oxidoreductase 23 kDa subunit, Complex I-23kD (CI-23kD), or TYKY subunit is an enzyme that in humans is encoded by the NDUFS8 gene. The NDUFS8 protein is a subunit of NADH dehydrogenase (ubiquinone) also known as Complex I, which is located in the mitochondrial inner membrane and is the largest of the five complexes of the electron transport chain. Mutations in this gene have been associated with Leigh syndrome.

<span class="mw-page-title-main">NDUFS7</span> Protein-coding gene in the species Homo sapiens

NADH dehydrogenase [ubiquinone] iron-sulfur protein 7, mitochondrial, also knowns as NADH-ubiquinone oxidoreductase 20 kDa subunit, Complex I-20kD (CI-20kD), or PSST subunit is an enzyme that in humans is encoded by the NDUFS7 gene. The NDUFS7 protein is a subunit of NADH dehydrogenase (ubiquinone) also known as Complex I, which is located in the mitochondrial inner membrane and is the largest of the five complexes of the electron transport chain.

<span class="mw-page-title-main">PRIM2</span> Protein-coding gene in the species Homo sapiens

DNA primase large subunit is an enzyme that in humans is encoded by the PRIM2 gene.

Mitochondrially encoded tRNA asparagine also known as MT-TN is a transfer RNA which in humans is encoded by the mitochondrial MT-TN gene.

Mitochondrially encoded tRNA tyrosine, also known as MT-TY, is a transfer RNA which in humans is encoded by the mitochondrial MT-TY gene.

<span class="mw-page-title-main">RNASEH2B</span> Protein-coding gene in the species Homo sapiens

Ribonuclease H2, subunit B is a protein in humans is encoded by the RNASEH2B gene. RNase H2 is composed of a single catalytic subunit (A) and two non-catalytic subunits, and degrades the RNA of RNA:DNA hybrids. The non-catalytic B subunit of RNase H2 is thought to play a role in DNA replication.

<span class="mw-page-title-main">Mitochondrial DNA depletion syndrome</span> Medical condition

Mitochondrial DNA depletion syndrome, or Alper's disease, is any of a group of autosomal recessive disorders that cause a significant drop in mitochondrial DNA in affected tissues. Symptoms can be any combination of myopathic, hepatopathic, or encephalomyopathic. These syndromes affect tissue in the muscle, liver, or both the muscle and brain, respectively. The condition is typically fatal in infancy and early childhood, though some have survived to their teenage years with the myopathic variant and some have survived into adulthood with the SUCLA2 encephalomyopathic variant. There is currently no curative treatment for any form of MDDS, though some preliminary treatments have shown a reduction in symptoms.

<span class="mw-page-title-main">PrimPol</span> Protein-coding gene in the species Homo sapiens

PrimPol is a protein encoded by the PRIMPOL gene in humans. PrimPol is a eukaryotic protein with both DNA polymerase and DNA Primase activities involved in translesion DNA synthesis. It is the first eukaryotic protein to be identified with priming activity using deoxyribonucleotides. It is also the first protein identified in the mitochondria to have translesion DNA synthesis activities.

<span class="mw-page-title-main">PRIM1</span> Protein-coding gene in the species Homo sapiens

DNA primase small subunit is an enzyme that in humans is encoded by the PRIM1 gene.

<span class="mw-page-title-main">DNA polymerase alpha catalytic subunit</span> Protein-coding gene in humans

DNA polymerase alpha catalytic subunit is an enzyme that in humans is encoded by the POLA1 gene.

References

  1. 1 2 3 GRCh38: Ensembl release 89: ENSG00000140521 – Ensembl, May 2017
  2. 1 2 3 GRCm38: Ensembl release 89: ENSMUSG00000039176 – 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. ↑ Zullo SJ, Butler L, Zahorchak RJ, Macville M, Wilkes C, Merril CR (Mar 1998). "Localization by fluorescence in situ hybridization (FISH) of human mitochondrial polymerase gamma (POLG) to human chromosome band 15q24→q26, and of mouse mitochondrial polymerase gamma (Polg) to mouse chromosome band 7E, with confirmation by direct sequence analysis of bacterial artificial chromosomes (BACs)". Cytogenetics and Cell Genetics. 78 (3–4): 281–4. doi:10.1159/000134672. PMID   9465903.
  6. 1 2 3 4 Entrez Gene: POLG polymerase (DNA directed), gamma, catalytic subunit PD-icon.svg This article incorporates text from this source, which is in the public domain .
  7. ↑ Yao, Daniel. "Cardiac Organellar Protein Atlas Knowledgebase (COPaKB) —— Protein Information". amino.heartproteome.org. Archived from the original on 2018-08-29. Retrieved 2018-08-28.
  8. ↑ Zong NC, Li H, Li H, Lam MP, Jimenez RC, Kim CS, Deng N, Kim AK, Choi JH, Zelaya I, Liem D, Meyer D, Odeberg J, Fang C, Lu HJ, Xu T, Weiss J, Duan H, Uhlen M, Yates JR, Apweiler R, Ge J, Hermjakob H, Ping P (October 2013). "Integration of cardiac proteome biology and medicine by a specialized knowledgebase". Circulation Research. 113 (9): 1043–53. doi:10.1161/CIRCRESAHA.113.301151. PMC   4076475 . PMID   23965338.
  9. 1 2 "POLG - DNA polymerase subunit gamma-1 - Homo sapiens (Human) - POLG gene & protein". www.uniprot.org. Retrieved 2018-08-28. Creative Commons by small.svg  This article incorporates text available under the CC BY 4.0 license.
  10. 1 2 "UniProt: the universal protein knowledgebase". Nucleic Acids Research. 45 (D1): D158–D169. January 2017. doi:10.1093/nar/gkw1099. PMC   5210571 . PMID   27899622.
  11. ↑ Ropp PA, Copeland WC (September 1996). "Cloning and characterization of the human mitochondrial DNA polymerase, DNA polymerase gamma". Genomics. 36 (3): 449–58. doi:10.1006/geno.1996.0490. PMID   8884268.
  12. ↑ Graziewicz MA, Longley MJ, Copeland WC (February 2006). "DNA polymerase gamma in mitochondrial DNA replication and repair". Chemical Reviews. 106 (2): 383–405. doi:10.1021/cr040463d. PMID   16464011.
  13. ↑ Giordano C, Powell H, Leopizzi M, De Curtis M, de Curtis M, Travaglini C, Sebastiani M, Gallo P, Taylor RW, d'Amati G (March 2009). "Fatal congenital myopathy and gastrointestinal pseudo-obstruction due to POLG1 mutations". Neurology. 72 (12): 1103–5. doi:10.1212/01.wnl.0000345002.47396.e1. PMC   2821839 . PMID   19307547.
  14. ↑ Müller-Höcker J, Horvath R, Schäfer S, Hessel H, Müller-Felber W, Kühr J, Copeland WC, Seibel P (February 2011). "Mitochondrial DNA depletion and fatal infantile hepatic failure due to mutations in the mitochondrial polymerase γ (POLG) gene: a combined morphological/enzyme histochemical and immunocytochemical/biochemical and molecular genetic study". Journal of Cellular and Molecular Medicine. 15 (2): 445–56. doi:10.1111/j.1582-4934.2009.00819.x. PMC   3822808 . PMID   19538466.
  15. ↑ Vermulst M, Bielas JH, Kujoth GC, Ladiges WC, Rabinovitch PS, Prolla TA, Loeb LA (April 2007). "Mitochondrial point mutations do not limit the natural lifespan of mice". Nature Genetics. 39 (4): 540–3. doi:10.1038/ng1988. PMID   17334366. S2CID   291780.
  16. ↑ "50 binary interactions found for search term POLG". IntAct Molecular Interaction Database. EMBL-EBI. Retrieved 2018-08-29.

Further reading

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