ATXN3 Antibody – Goat Polyclonal

Machado-Joseph disease, also known as spinocerebellar ataxia-3, is an autosomal dominant neurologic disorder. The protein encoded by this gene contains (CAG)n repeats in the coding region, and the expansion of these repeats from the normal 13-36 to 68-79 is one cause of Machado-Joseph disease. There is a negative correlation between the age of onset and CAG repeat numbers. Alternatively spliced transcript variants encoding different isoforms have been described for this gene. [provided by RefSeq, Sep 2009]

Function: Deubiquitinating enzyme involved in protein homeostasis maintenance, transcription, cytoskeleton regulation, myogenesis and degradation of misfolded chaperone substrates. Binds long polyubiquitin chains and trims them, while it has weak or no activity against chains of 4 or less ubiquitins. Involved in degradation of misfolded chaperone substrates via its interaction with STUB1/CHIP: recruited to monoubiquitinated STUB1/CHIP, and restricts the length of ubiquitin chain attached to STUB1/CHIP substrates and preventing further chain extension. In response to misfolded substrate ubiquitination, mediates deubiquitination of monoubiquitinated STUB1/CHIP. Interacts with key regulators of transcription and represses transcription: acts as a histone-binding protein that regulates transcription. Ref.9 Ref.10 Ref.12 Ref.16

Catalytic activity: Thiol-dependent hydrolysis of ester, thioester, amide, peptide and isopeptide bonds formed by the C-terminal Gly of ubiquitin (a 76-residue protein attached to proteins as an intracellular targeting signal). Ref.10

Subunit structure: Interacts with STUB1/CHIP (when monoubiquitinated)

By similarity. Interacts with DNA repair proteins RAD23A and RAD23B.

Subcellular location: Nucleus matrix. Note: Predominantly nuclear, but not exclusively, inner nuclear matrix. Ref.8

Tissue specificity: Ubiquitous.

Domain: The UIM domains bind ubiquitin and interact with various E3 ubiquitin-protein ligase, such as STUB1/CHIP. They are essential to limit the length of ubiquitin chains

By similarity.

Post-translational modification: Monoubiquitinated N-terminally by UBE2W, possibly leading to activate the deubiquitinating enzyme activity.

Polymorphism: The poly-Gln region of ATXN3 is highly polymorphic (14 to 41 repeats) in the normal population and is expanded to about 55-82 repeats in spinocerebellar ataxia 3 (SCA3) patients.The MJD1a allele carries a single nucleotide substitution in codon 349 generating a stop codon instead of a Tyr. In the Japanese population, the MJD1a allele seems to be significantly associated with Gln expansion.

Involvement in disease: Spinocerebellar ataxia 3 (SCA3) [MIM:109150]: Spinocerebellar ataxia is a clinically and genetically heterogeneous group of cerebellar disorders. Patients show progressive incoordination of gait and often poor coordination of hands, speech and eye movements, due to cerebellum degeneration with variable involvement of the brainstem and spinal cord. SCA3 belongs to the autosomal dominant cerebellar ataxias type I (ADCA I) which are characterized by cerebellar ataxia in combination with additional clinical features like optic atrophy, ophthalmoplegia, bulbar and extrapyramidal signs, peripheral neuropathy and dementia. The molecular defect in SCA3 is the a CAG repeat expansion in ATX3 coding region. Longer expansions result in earlier onset and more severe clinical manifestations of the disease.Note: The disease is caused by mutations affecting the gene represented in this entry. Ref.1

Sequence similarities: Contains 1 Josephin domain.Contains 3 UIM (ubiquitin-interacting motif) repeats.