NUP120P - A YEAST NUCLEOPORIN REQUIRED FOR NPC DISTRIBUTION AND MESSENGER-RNA TRANSPORT

To extend our understanding of the mechanism by which the nuclear pore complex (NPC) mediates macromolecular transport across the nuclear en velope we have focused on defining the composition and molecular organ ization of the yeast NPC. Peptide sequence analysis of a polypeptide w ith a M(r) of similar to 100,000 present in a highly enriched yeast NP C fraction identified a novel yeast nucleoporin we term Nup120p. Nup12 0p corresponds to the open reading frame (ORF) YKL057c identified by t he yeast genome sequencing project. The ORF predicts a protein with a calculated molecular mass of 120.5 kD containing two leucine zipper mo tifs, a short coiled-coil region and limited primary sequence similari ty to Nup133p. Nup120p was localized to the NPC using a protein A-tagg ed chimera in situ by indirect immunofluorescence microscopy. Deletion of the NUP120 gene caused clustering of NPCs at one side of the nucle ar envelope, moderate nucleolar fragmentation and slower cell growth. Transfer of nup120 Delta cells to 37 degrees C resulted in the nuclear accumulation of poly(A)(+) mRNA, extensive fragmentation of the nucle olus, spindle defects, and cell death.