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Genetics Home Reference: your guide to understanding genetic conditions
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POLR3B

Reviewed June 2013

What is the official name of the POLR3B gene?

The official name of this gene is “polymerase (RNA) III (DNA directed) polypeptide B.”

POLR3B is the gene's official symbol. The POLR3B gene is also known by other names, listed below.

What is the normal function of the POLR3B gene?

The POLR3B gene provides instructions for making one part (subunit) of an enzyme called RNA polymerase III. This enzyme is involved in the production (synthesis) of ribonucleic acid (RNA), a chemical cousin of DNA. The RNA polymerase III enzyme attaches (binds) to DNA and synthesizes RNA in accordance with the instructions carried by the DNA, a process called transcription. RNA polymerase III helps synthesize several forms of RNA, including ribosomal RNA (rRNA) and transfer RNA (tRNA). Molecules of rRNA and tRNA assemble protein building blocks (amino acids) into working proteins; this process is essential for the normal functioning and survival of cells.

Does the POLR3B gene share characteristics with other genes?

The POLR3B gene belongs to a family of genes called POLR (RNA polymerase subunits).

A gene family is a group of genes that share important characteristics. Classifying individual genes into families helps researchers describe how genes are related to each other. For more information, see What are gene families? (http://ghr.nlm.nih.gov/handbook/howgeneswork/genefamilies) in the Handbook.

How are changes in the POLR3B gene related to health conditions?

Pol III-related leukodystrophy - caused by mutations in the POLR3B gene

At least 10 POLR3B gene mutations have been associated with Pol III-related leukodystrophy. Leukodystrophies are conditions that involve abnormalities of the nervous system's white matter. White matter consists of nerve fibers covered by a fatty substance called myelin, which insulates nerve fibers and promotes the rapid transmission of nerve impulses. A reduced ability to form myelin (hypomyelination) leads to the signs and symptoms of Pol III-related leukodystrophy, which include intellectual disability and difficulty with coordinating movements (ataxia). Development of the teeth (dentition) is also abnormal in this disorder.

In the Pol III-related leukodystrophies, POLR3B gene mutations may impair the ability of the subunits of the RNA polymerase III enzyme to assemble properly or result in an RNA polymerase III with impaired ability to bind to DNA. Reduced function of the RNA polymerase III molecule likely affects development and function of many parts of the body, but the relationship between POLR3B gene mutations and the specific signs and symptoms of these disorders is unknown.

People with Pol III-related leukodystrophy may have different combinations of its signs and symptoms. These varied combinations of clinical features were originally described as separate disorders. Affected individuals may be diagnosed with ataxia, delayed dentition, and hypomyelination (ADDH); hypomyelination, hypodontia, hypogonadotropic hypogonadism (4H syndrome); tremor-ataxia with central hypomyelination (TACH); leukodystrophy with oligodontia (LO); or hypomyelination with cerebellar atrophy and hypoplasia of the corpus callosum (HCAHC). Because these disorders were later found to have the same genetic cause, researchers now group them as variations of the single condition Pol III-related leukodystrophy.

Where is the POLR3B gene located?

Cytogenetic Location: 12q23.3

Molecular Location on chromosome 12: base pairs 106,357,657 to 106,510,197

The POLR3B gene is located on the long (q) arm of chromosome 12 at position 23.3.

The POLR3B gene is located on the long (q) arm of chromosome 12 at position 23.3.

More precisely, the POLR3B gene is located from base pair 106,357,657 to base pair 106,510,197 on chromosome 12.

See How do geneticists indicate the location of a gene? (http://ghr.nlm.nih.gov/handbook/howgeneswork/genelocation) in the Handbook.

Where can I find additional information about POLR3B?

You and your healthcare professional may find the following resources about POLR3B helpful.

You may also be interested in these resources, which are designed for genetics professionals and researchers.

What other names do people use for the POLR3B gene or gene products?

  • C128
  • DNA-directed RNA polymerase III 127.6 kDa polypeptide
  • DNA-directed RNA polymerase III subunit B
  • DNA-directed RNA polymerase III subunit RPC2
  • DNA-directed RNA polymerase III subunit RPC2 isoform 1
  • DNA-directed RNA polymerase III subunit RPC2 isoform 2
  • FLJ10388
  • HLD8
  • RNA polymerase III subunit C2
  • RPC2
  • RPC2_HUMAN

See How are genetic conditions and genes named? (http://ghr.nlm.nih.gov/handbook/mutationsanddisorders/naming) in the Handbook.

What glossary definitions help with understanding POLR3B?

acids ; ataxia ; atrophy ; corpus callosum ; DNA ; DNA-directed RNA polymerase ; enzyme ; gene ; hypodontia ; hypogonadism ; hypogonadotropic ; hypoplasia ; leukodystrophy ; molecule ; nervous system ; oligodontia ; protein ; ribonucleic acid ; ribosomal RNA ; RNA ; RNA polymerase ; subunit ; syndrome ; synthesis ; transcription ; transfer RNA ; tremor ; tRNA ; white matter

You may find definitions for these and many other terms in the Genetics Home Reference Glossary (http://www.ghr.nlm.nih.gov/glossary).

References

  • Daoud H, Tétreault M, Gibson W, Guerrero K, Cohen A, Gburek-Augustat J, Synofzik M, Brais B, Stevens CA, Sanchez-Carpintero R, Goizet C, Naidu S, Vanderver A, Bernard G. Mutations in POLR3A and POLR3B are a major cause of hypomyelinating leukodystrophies with or without dental abnormalities and/or hypogonadotropic hypogonadism. J Med Genet. 2013 Mar;50(3):194-7. doi: 10.1136/jmedgenet-2012-101357. Epub 2013 Jan 25. (http://www.ncbi.nlm.nih.gov/pubmed/23355746?dopt=Abstract)
  • NCBI Gene (http://www.ncbi.nlm.nih.gov/gene/55703)
  • OMIM: POLYMERASE III, RNA, SUBUNIT B (http://omim.org/entry/614366)
  • Saitsu H, Osaka H, Sasaki M, Takanashi J, Hamada K, Yamashita A, Shibayama H, Shiina M, Kondo Y, Nishiyama K, Tsurusaki Y, Miyake N, Doi H, Ogata K, Inoue K, Matsumoto N. Mutations in POLR3A and POLR3B encoding RNA Polymerase III subunits cause an autosomal-recessive hypomyelinating leukoencephalopathy. Am J Hum Genet. 2011 Nov 11;89(5):644-51. doi: 10.1016/j.ajhg.2011.10.003. Epub 2011 Oct 27. (http://www.ncbi.nlm.nih.gov/pubmed/22036171?dopt=Abstract)
  • Tétreault M, Choquet K, Orcesi S, Tonduti D, Balottin U, Teichmann M, Fribourg S, Schiffmann R, Brais B, Vanderver A, Bernard G. Recessive mutations in POLR3B, encoding the second largest subunit of Pol III, cause a rare hypomyelinating leukodystrophy. Am J Hum Genet. 2011 Nov 11;89(5):652-5. doi: 10.1016/j.ajhg.2011.10.006. Epub 2011 Oct 27. (http://www.ncbi.nlm.nih.gov/pubmed/22036172?dopt=Abstract)
  • Vanderver A, Tonduti D, Bernard G, Lai J, Rossi C, Carosso G, Quezado M, Wong K, Schiffmann R. More than hypomyelination in Pol-III disorder. J Neuropathol Exp Neurol. 2013 Jan;72(1):67-75. doi: 10.1097/NEN.0b013e31827c99d2. (http://www.ncbi.nlm.nih.gov/pubmed/23242285?dopt=Abstract)

 

The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? (http://ghr.nlm.nih.gov/handbook/consult/findingprofessional) in the Handbook.

 
Reviewed: June 2013
Published: April 17, 2014