Ataxin 3Ataxin-3 is a protein that in humans is encoded by the ATXN3 gene.Clinical significanceMachado–Joseph disease, also known as spinocerebellar ataxia type 3, is an autosomal dominant neurologic disorder. The protein encoded by the ATXN3 gene contains CAG repeats in the coding region, and the expansion of these repeats from the normal 13-36 to 68-79 is the cause of Machado–Joseph disease. This disorder is thus a trinucleotide repeat disorder type I known as a polyglutamine (PolyQ) disease. There is an inverse correlation between the age of onset and CAG repeat numbers. Alternatively spliced transcript variants encoding different isoforms have been described for this gene.InteractionsAtaxin 3 has been shown to interact with: RAD23A, RAD23B, and VCP.