摘要 : Rat7p/Nup159p is an essential nucleoporin of Saccharomyces cerevisiae originally isolated in a genetic screen designed to identify yeast temperature-sensitive mutants defective in mRNA export, Here we describe a detailed structura... 展开 Rat7p/Nup159p is an essential nucleoporin of Saccharomyces cerevisiae originally isolated in a genetic screen designed to identify yeast temperature-sensitive mutants defective in mRNA export, Here we describe a detailed structural-functional analysis of Rat7p/Nup159p. The mutation in the rat7-1 ts allele, isolated in the original genetic screen, was found to be a single base pair change that created a stop codon approximately 100 amino acids upstream of the actual stop codon of this 1,460 amino acid polypeptide, thus eliminating one of the two predicted coiled-coil regions located near the carboxyl terminus of the protein, These coiled-coil regions are essential since an allele lacking both coiled-coil regions was unable to support growth under any conditions, In contrast, no other region of the protein was absolutely required, The SAFG/PSFG repeat region in the central third of the protein was completely dispensable for growth at temperatures between 16 degrees C and 37 degrees C and cells expressing this mutant allele were indistinguishable from wild type, Deletion of the aminoterminal third of the protein, upstream from the repeat region, or the portion between the repeat region and the coiled-coils resulted in temperature-sensitivity, but the two alleles showed distinct phenotypes with respect to the behavior of nuclear pore complexes (NPCs), Taken together, our data suggest that Rat7p/Nup159p is anchored within the NPC through its coiled-coil region and adjacent sequences, In addition, we postulate that the N-terminal third of Rat7p/Nup159p plays an important role in mRNA export. [References: 55] 收起