Fig. 4. Overexpression of YRB2 is toxic. (A) Overexpression of YRB2 causes the mislocalization of 5' ITS1. 5' IST1 was localized in wild-type cells containing pGAL vector (b) or pGAL-YRB2 (d) after 1 hour induction with galactose. Chromosomal DNA was labeled with DAPI (a,c). Arrows point to DAPI-stained chromatin while arrowheads point to the nucleolus. Magnified views of two cells are shown below each panel. (B) High-copy expression of YRB2 inhibits the growth of rat2-1/nup120 cells. rat2-1 (PSY209) or wild-type (PSY580) cells containing 2µ vector (pPS701), full-length YRB2 (pPS2096), N-terminal truncation (pPS2104), deletion of the Nup FG motifs (pPS2105), or the C-terminal/Ran-binding domain truncation (pPS2106) were grown on trp^- dropout plates at 25°C.