Fig. 6.

RPAP4/GPN1 function in POLR2A/RPB1 nuclear import is coupled to microtubule assembly. A, treatment of yeast cells (WT strain) with benomyl (60 μg/ml) leads to accumulation of POLR2A/RPB1 in the cytoplasm. B, treatment of HeLa cells with benomyl at concentrations (30 μg/ml) that produce microtubule dismantling (right panel) leads to accumulation of POLR2A/RPB1 in the cytoplasm (left panel). C, NPA3 mutant yeast strains with a slow growth phenotype are hypersensitive to the microtubule assembly inhibitor benomyl. Yeast strains expressing NPA3 variants with amino acid substitutions in the G1 (K16R), G2 (D40E), and GPN loop (G70A and N72Q) and showing slow growth phenotypes (see Fig. 2B) were grown in the absence or the presence of sublethal concentrations of benomyl (20 μg/ml). DIC, differential interference contrast.