ATXN1

The autosomal dominant cerebellar ataxias (ADCA) are a heterogeneous group of neurodegenerative disorders characterized by progressive degeneration of the cerebellum, brain stem and spinal cord. Clinically, ADCA has been divided into three groups: ADCA types I-III. ADCAI is genetically heterogeneous, with five genetic loci, designated spinocerebellar ataxia (SCA) 1, 2, 3, 4 and 6, being assigned to five different chromosomes. ADCAII, which always presents with retinal degeneration (SCA7), and ADCAIII often referred to as the `pure' cerebellar syndrome (SCA5), are most likely homogeneous disorders. Several SCA genes have been cloned and shown to contain CAG repeats in their coding regions. ADCA is caused by the expansion of the CAG repeats, producing an elongated polyglutamine tract in the corresponding protein. The expanded repeats are variable in size and unstable, usually increasing in size when transmitted to successive generations. The function of the ataxins is not known. This locus has been mapped to chromosome 6, and it has been determined that the diseased allele contains 40-83 CAG repeats, compared to 6-39 in the normal allele, and is associated with spinocerebellar ataxia type 1 (SCA1). Alternative splicing results in multiple transcript variants, with one variant encoding multiple distinct proteins, ATXN1 and Alt-ATXN1, due to the use of overlapping alternate reading frames. [provided by RefSeq, Nov 2017]

Full Name

Ataxin 1

Function

Chromatin-binding factor that repress Notch signaling in the absence of Notch intracellular domain by acting as a CBF1 corepressor. Binds to the HEY promoter and might assist, along with NCOR2, RBPJ-mediated repression. Binds RNA in vitro. May be involved in RNA metabolism (PubMed:21475249).
In concert with CIC and ATXN1L, involved in brain development (By similarity).

Biological Process

Anatomical structure development Source: GO_Central
Brain development Source: UniProtKB
Learning Source: UniProtKB
Memory Source: UniProtKB
Negative regulation of transcription, DNA-templated Source: UniProtKB
Negative regulation of transcription by RNA polymerase II Source: GO_Central
Nervous system development Source: GO_Central
Nuclear export Source: UniProtKB
Regulation of transcription, DNA-templated Source: GO_Central
RNA processing Source: UniProtKB
Social behavior Source: UniProtKB

Cellular Location

Cytoplasm; Nucleus. Colocalizes with USP7 in the nucleus.

Involvement in disease

Spinocerebellar ataxia 1 (SCA1): The disease is caused by variants affecting the gene represented in this entry. The disease is caused by expansion of the polyglutamine tract to about 40-83 repeats, causing accumulation in neurons and exerting toxicity. 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. SCA1 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. SCA1 is caused by expansion of a CAG repeat in the coding region of ATXN1. Longer expansions result in earlier onset and more severe clinical manifestations of the disease.

PTM

Ubiquitinated by UBE3A, leading to its degradation by the proteasome. The presence of expanded poly-Gln repeats in spinocerebellar ataxia 1 (SCA1) patients impairs ubiquitination and degradation, leading to accumulation of ATXN1 in neurons and subsequent toxicity.
Phosphorylation at Ser-775 increases the pathogenicity of proteins with an expanded polyglutamine tract.
Sumoylation is dependent on nuclear localization and phosphorylation at Ser-775. It is reduced in the presence of an expanded polyglutamine tract.