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. Defects in ATXN7 are the cause of spinocerebellar ataxia type 7 (SCA7); also known as olivopontocerebellar atrophy III (OPCA III or OPCA3) or olivopontocerebellar atrophy with retinal degeneration. 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. Belongs to the ataxin-7 family. 2 isoforms of the human protein are produced by alternative splicing. Note: This description may include information from UniProtKB.