In Huntington's disease, CAG repeat expansion of the Huntingtin gene produces mutant RNA and mutant protein containing elongated polyglutamine tract, which causes dysfunction and cell death of neurons. From our reseach of Huntington's disease and other polyglutamine diseases for nearly 20 years, we identified new disease-related genes including PQBP1, Ku70, HMGB, Maxer, and Omi. Through the analysis of these molecules, we unraveled new pathomechanisms deeply linked to nuclear functions such as transcription, splicing, DNA damage repair. These findings will become the basis to develop new molecule targeted therapeutics.