PQBP-1/Npw38, a nuclear protein binding to the polyglutamine tract, interacts with US-15kD/dim1p via the carboxyl-terminal domain

PQBP-1 was identified as a binding protein to the polyglutamine tract prese nt in various transcription-related factors and causative genes for neurode generative disorders. This novel gene contains at least two functional doma ins, WW domain and carboxyl-terminal domain (CTD), strictly conserved beyon d species. Although human PQBP-1 additionally contains the polar amino acid -rich domain by which it binds to the polyglutamine tract, genuine physiolo gical function(s) have not been clarified. In this study, we showed that U5 -15kD, human homologue of fission yeast dim1p, is a partner molecule of PQB P-1 binding to CTD. This finding suggests physiological functions of PQBP-1 in splicing, cell cycle, and ubiquitination, through which we can speculat e the pathological roles of PQBP-1 in triplet repeat diseases. (C) 2000 Aca demic Press.