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Genetics Home Reference: your guide to understanding genetic conditions     A service of the U.S. National Library of Medicine®


Reviewed February 2011

What is the official name of the ATXN3 gene?

The official name of this gene is “ataxin 3.”

ATXN3 is the gene's official symbol. The ATXN3 gene is also known by other names, listed below.

What is the normal function of the ATXN3 gene?

The ATXN3 gene provides instructions for making an enzyme called ataxin-3, which is found in cells throughout the body. Ataxin-3 is involved in a mechanism called the ubiquitin-proteasome system that destroys and gets rid of excess or damaged proteins. The molecule ubiquitin attaches (binds) to unneeded proteins and tags them to be broken down (degraded) within cells. Ataxin-3 removes (cleaves) the ubiquitin from these unwanted proteins just before they are degraded so that the ubiquitin can be used again. Due to its role in cleaving ubiquitin from proteins, ataxin-3 is known as a deubiquitinating enzyme.

Researchers believe that ataxin-3 also may be involved in regulating the first stage of protein production (transcription).

How are changes in the ATXN3 gene related to health conditions?

spinocerebellar ataxia type 3 - caused by mutations in the ATXN3 gene

Spinocerebellar ataxia type 3 (SCA3) is a condition characterized by progressive problems with movement. SCA3 results from a mutation in the ATXN3 gene known as a trinucleotide repeat expansion. This mutation increases the length of the repeated CAG segment in the ATXN3 gene. People with SCA3 have more than 50 CAG repeats.

The expanded CAG segment leads to the production of an abnormally long version of the ataxin-3 protein that folds into the wrong 3-dimensional shape. This nonfunctional ataxin-3 protein cannot remove ubiquitin from proteins that are no longer needed. As a result, these unwanted proteins, along with ubiquitin and ataxin-3, cluster together to form clumps (aggregates) within the nucleus of the cells. It is unclear how these aggregates affect cell function, because they are found in healthy cells as well as those that die.

Nerve cells (neurons) and other types of brain cells are most affected by mutations in the ATXN3 gene. SCA3 is associated with cell death in the part of the brain that is connected to the spinal cord (the brainstem), the part of the brain involved in coordinating movements (the cerebellum), and other areas of the brain. This condition is also associated with the death of neurons in the spinal cord. Over time, the loss of cells in the brain and spinal cord cells cause the signs and symptoms characteristic of SCA3.

Where is the ATXN3 gene located?

Cytogenetic Location: 14q21

Molecular Location on chromosome 14: base pairs 92,058,552 to 92,106,621

(Homo sapiens Annotation Release 107, GRCh38.p2) (NCBI (

The ATXN3 gene is located on the long (q) arm of chromosome 14 at position 21.

The ATXN3 gene is located on the long (q) arm of chromosome 14 at position 21.

More precisely, the ATXN3 gene is located from base pair 92,058,552 to base pair 92,106,621 on chromosome 14.

See How do geneticists indicate the location of a gene? ( in the Handbook.

Where can I find additional information about ATXN3?

You and your healthcare professional may find the following resources about ATXN3 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 ATXN3 gene or gene products?

  • AT3
  • ataxin-3
  • ATX3

See How are genetic conditions and genes named? ( in the Handbook.

What glossary definitions help with understanding ATXN3?

ataxia ; brainstem ; cell ; cerebellum ; enzyme ; gene ; molecule ; mutation ; nucleus ; proteasome ; protein ; stage ; transcription ; trinucleotide repeat ; ubiquitin

You may find definitions for these and many other terms in the Genetics Home Reference Glossary.


  • OMIM: ATAXIN 3 (
  • D'Abreu A, França MC Jr, Paulson HL, Lopes-Cendes I. Caring for Machado-Joseph disease: current understanding and how to help patients. Parkinsonism Relat Disord. 2010 Jan;16(1):2-7. doi: 10.1016/j.parkreldis.2009.08.012. Epub 2009 Oct 6. Review. (
  • Haacke A, Broadley SA, Boteva R, Tzvetkov N, Hartl FU, Breuer P. Proteolytic cleavage of polyglutamine-expanded ataxin-3 is critical for aggregation and sequestration of non-expanded ataxin-3. Hum Mol Genet. 2006 Feb 15;15(4):555-68. Epub 2006 Jan 11. (
  • NCBI Gene (
  • Nicastro G, Masino L, Esposito V, Menon RP, De Simone A, Fraternali F, Pastore A. Josephin domain of ataxin-3 contains two distinct ubiquitin-binding sites. Biopolymers. 2009 Dec;91(12):1203-14. doi: 10.1002/bip.21210. (


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? ( in the Handbook.

Reviewed: February 2011
Published: February 1, 2016