ATXN3
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).
The poly-Gln domain is involved in the interaction with BECN1 and subsequent starvation-induced autophagy (PubMed:28445460).
Function
Deubiquitinating enzyme involved in protein homeostasis maintenance, transcription, cytoskeleton regulation, myogenesis and degradation of misfolded chaperone substrates (PubMed:12297501, PubMed:16118278, PubMed:17696782, PubMed:23625928, PubMed:28445460, PubMed:33157014). Binds long polyubiquitin chains and trims them, while it has weak or no activity against chains of 4 or less ubiquitins (PubMed:17696782). 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 (By similarity). Interacts with key regulators of transcription and represses transcription: acts as a histone-binding protein that regulates transcription (PubMed:12297501). Acts as a negative regulator of mTORC1 signaling in response to amino acid deprivation by mediating deubiquitination of RHEB, thereby promoting RHEB inactivation by the TSC-TBC complex (PubMed:33157014). Regulates autophagy via the deubiquitination of 'Lys-402' of BECN1 leading to the stabilization of BECN1 (PubMed:28445460).
Involvement in disease
Spinocerebellar ataxia 3
SCA3
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.
None
The disease is caused by variants affecting the gene represented in this entry.
Post-translational modifications
Monoubiquitinated N-terminally by UBE2W, possibly leading to activate the deubiquitinating enzyme activity (PubMed:23696636).
Tissue Specificity
Ubiquitous.
Cellular localization
- Nucleus matrix
- Nucleus
- Lysosome membrane
- Peripheral membrane protein
- Predominantly nuclear, but not exclusively, inner nuclear matrix (PubMed:9580663). Recruited to lysosomal membrane in response to amino acid deprivation by the RagA/RRAGA-RagB/RRAGB complex (PubMed:33157014).
Alternative names
ATX3, MJD, MJD1, SCA3, ATXN3, Ataxin-3, Machado-Joseph disease protein 1, Spinocerebellar ataxia type 3 protein