The Saccharomyces cerevisiae small GTPase, Gsp1p/Ran, is involved in 3' processing of 7S-to-5.8S rRNA and in degradation of the excised 5'-A0 fragment of 35S pre-rRNA, both of which are carried out by the exosome.
Dis3p, a subunit of the exosome, interacts directly with Ran. To clarify the relationship between the exosome and the RanGTPase cycle, a series of temperature-sensitive Saccharomyces cerevisiae dis3 mutants were isolated and their 5.8S rRNA processing was compared with processing in strains with mutations in a S. cerevisiae Ran homologue, Gsp1p. In both dis3 and gsp1 mutants, 3' processing of 7S-to-5.8S rRNA was blocked at three identical sites in an allele-specific manner. In contrast, the 5' end of 5.8S rRNA was terminated normally in gsp1 and in dis3. Inhibition of 5.8S rRNA maturation in gsp1 was rescued by overexpression of nuclear exosome components Dis3p, Rrp4p, and Mtr4p, but not by a cytoplasmic exosome component, Ski2p. Furthermore, gsp1 and dis3 accumulated the 5'-A0 fragment of 35S pre-rRNA, which is also degraded by the exosome, and the level of 27S rRNA was reduced. Neither 5.8S rRNA intermediates nor 5'-A0 fragments were observed in mutants defective in the nucleocytoplasmic transport, indicating that Gsp1p regulates rRNA processing through Dis3p, independent of nucleocytoplasmic transport.
Suzuki
N
N
Department of Molecular Biology, Graduate School of Medical Science, Kyushu University, 3-1-1 Maedashi, Higashiku, Fukuoka 812-8582, Japan.
Noguchi
E
E
Nakashima
N
N
Oki
M
M
Ohba
T
T
Tartakoff
A
A
Ohishi
M
M
Nishimoto
T
T
D021581:Active Transport, Cell Nucleus; D000483:Alleles; D002467:Cell Nucleus / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D053487:DEAD-box RNA Helicases; D017931:DNA Primers / Q000378:metabolism; D005095:Exoribonucleases; D063326:Exosome Multienzyme Ribonuclease Complex; D005656:Fungal Proteins / Q000235:genetics; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D005838:Genotype; D008957:Models, Genetic; D020559:Monomeric GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D010957:Plasmids / Q000378:metabolism; D016133:Polymerase Chain Reaction; D020365:RNA Helicases / Q000378:metabolism; D012326:RNA Splicing; D012333:RNA, Messenger / Q000378:metabolism; D012335:RNA, Ribosomal / Q000378:metabolism; D012340:RNA, Ribosomal, 5.8S / Q000378:metabolism*; D020733:RNA, Small Cytoplasmic / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D018271:Signal Recognition Particle / Q000378:metabolism*; D013696:Temperature; D013997:Time Factors
C115990:7SL RNA; D017931:DNA Primers; D005656:Fungal Proteins; C080324:GSP1 protein, S cerevisiae; D009687:Nuclear Proteins; D012333:RNA, Messenger; D012335:RNA, Ribosomal; D012340:RNA, Ribosomal, 5.8S; D020733:RNA, Small Cytoplasmic; D016601:RNA-Binding Proteins; D029701:Saccharomyces cerevisiae Proteins; D018271:Signal Recognition Particle; D005095:Exoribonucleases; D063326:Exosome Multienzyme Ribonuclease Complex; C542283:DIS3 protein, S cerevisiae; D020558:GTP Phosphohydrolases; C101004:MTR4 protein, S cerevisiae; D053487:DEAD-box RNA Helicases; D020365:RNA Helicases; D020559:Monomeric GTP-Binding Proteins