CHARACTERIZATION OF A NUCLEAR-PROTEIN CONFERRING BREFELDIN-A RESISTANCE IN SCHIZOSACCHAROMYCES-POMBE

The fungal metabolite brefeldin A disrupts protein secretion and cause s the redistribution of the Golgi complex 60 the endoplasmic reticulum . Previously we isolated six genes that, when present in multiple copi es, confer brefeldin A resistance 60 wild type Schizosaccharomyces pom be. Here we describe the characterization of one of these genes, hba1. This gene encodes an essential protein that shares homology with the mammalian protein RanBP1 and the protein encoded by the Saccharomyces cerevisiae gene YRB1 and contains a peptide motif present in several p roteins found within the nuclear pore complex. The protein encoded by hba1 is localized to the nucleus, and it was determined that this prot ein is phosphorylated in vivo. The characterization of hba1 thus demon strates a novel mechanism of drug resistance in S. pombe.