Characterization of a nuclear protein conferring brefeldin A resistance in Schizosaccharomyces pombe.

The fungal metabolite brefeldin A disrupts protein secretion and causes the redistribution of the Golgi complex to the endoplasmic reticulum. Previously we isolated six genes that, when present in multiple copies, confer brefeldin A resistance to wild type Schizosaccharomyces pombe. 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 proteins found within the nuclear pore complex. The protein encoded by hba1 is localized to the nucleus, and it was determined that this protein is phosphorylated in vivo. The characterization of hba1 thus demonstrates a novel mechanism of drug resistance in S. pombe.