ATXN3 and Machado-Joseph disease: However, aside from its involvement in MJD, the ataxin-3 protein is intimately involved in an eclectic range of biological processes ranging from protein quality control [10,11], autophagy [12], transcription regulation [13,14], cytoskeletal regulation [15,16], stress responses [17], and antiviral response [18], to DNA repair [19].