ATXN7

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. This locus has been mapped to chromosome 3, and it has been determined that the diseased allele associated with spinocerebellar ataxia-7 contains 37-306 CAG repeats (near the N-terminus), compared to 4-35 in the normal allele. The encoded protein is a component of the SPT3/TAF9/GCN5 acetyltransferase (STAGA) and TBP-free TAF-containing (TFTC) chromatin remodeling complexes, and it thus plays a role in transcriptional regulation.

Ataxin 7

Acts as component of the STAGA transcription coactivator-HAT complex. Mediates the interaction of STAGA complex with the CRX and is involved in CRX-dependent gene activation. Necessary for microtubule cytoskeleton stabilization.

Histone deubiquitination Source: UniProtKB
Microtubule cytoskeleton organization Source: UniProtKB
Negative regulation of microtubule depolymerization Source: CACAO
Nucleus organization Source: ProtInc
Protein deubiquitination Source: Reactome
Visual perception Source: ProtInc

Isoform a: Cytoskeleton; Nucleus; Nucleolus; Nucleus matrix. In addition to a diffuse distribution throughout the nucleus, it is associated with the nuclear matrix and the nucleolus. It is able to shuttle between the nucleus and cytoplasm.
Isoform b: Cytoplasm

Spinocerebellar ataxia 7 (SCA7): 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 degeneration of the cerebellum with variable involvement of the brainstem and spinal cord. SCA7 belongs to the autosomal dominant cerebellar ataxias type II (ADCA II) which are characterized by cerebellar ataxia with retinal degeneration and pigmentary macular dystrophy.

Proteolytically cleaved. The cleavage may be involved in SCA7 degeneration: the isoform fragments may exert distinct toxic influences that could contribute to selective neurodegeneration.
Sumoylation decreases the aggregation propensity and cellular toxicity of forms with an expanded poly-Gln region but has no effect on subcellular location or interaction with components of the STAGA complex.