Differential export requirements for shuttling serine/arginine-type mRNA-binding proteins.
Messenger RNAs are transported to the cytoplasm bound to several shuttling mRNA-binding proteins. Here, we present the characterization of Hrb1, a novel component of the transported ribonucleoprotein complex in Saccharomyces cerevisiae. The protein is similar to the other two serine/arginine (SR)-type proteins in yeast, Gbp2 and Npl3. Hrb1 is nuclear at steady state and its import is mediated by the karyopherin Mtr10. Hrb1 binds to poly(A)+ RNA in vivo and its binding is significantly increased in MTR10 mutants, suggesting a role for Mtr10 in dissociating Hrb1 from the mRNAs. Interestingly, by comparing the export requirements of all three SR proteins we find similarities but also striking differences. While the export of all three proteins is dependent on the export of mRNAs in general, as no transport is observed in mutants defective in transcription (rpb1-1) or mRNA export (mex67-5), we find specific requirements for components of the THO complex, involved in transcription elongation. While both Hrb1 and Gbp2 depend on Mft1 and Hpr1 for their nuclear export, Npl3 is exported independently of both proteins. These findings suggest that Hrb1 and Gbp2, but not Npl3, might be loaded onto the growing mRNA via the THO complex components Mtf1 and Hrp1.
Häcker
Sabine
S
Philipps-Universität Marburg, Institut für Molekularbiologie und Tumorforschung, Emil-Mannkopff-Strasse 2, 35037 Marburg, Germany.
Krebber
Heike
H
D001120:Arginine / Q000737:chemistry*; D001692:Biological Transport; D002467:Cell Nucleus / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D049452:Green Fluorescent Proteins; D034441:Heterogeneous-Nuclear Ribonucleoproteins / Q000737:chemistry / Q000502:physiology; D008164:Luminescent Proteins / Q000378:metabolism; D024101:Mitochondrial Proteins; D009154:Mutation; D009687:Nuclear Proteins; D029543:Nucleocytoplasmic Transport Proteins / Q000378:metabolism; D010957:Plasmids / Q000378:metabolism; D011061:Poly A / Q000378:metabolism; D039102:Poly(A)-Binding Proteins; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000737:chemistry* / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology; D012694:Serine / Q000737:chemistry*; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic; D014466:Ultraviolet Rays
C474034:Gbp2 protein, S cerevisiae; C063494:HPR1 protein, S cerevisiae; D034441:Heterogeneous-Nuclear Ribonucleoproteins; C089362:Hrb1 protein, S cerevisiae; D008164:Luminescent Proteins; C071720:MTF1 protein, S cerevisiae; C110033:MTR10 protein, S cerevisiae; D024101:Mitochondrial Proteins; D009687:Nuclear Proteins; D029543:Nucleocytoplasmic Transport Proteins; D039102:Poly(A)-Binding Proteins; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D049452:Green Fluorescent Proteins; D011061:Poly A; D012694:Serine; D001120:Arginine; C490216:SKY1 protein, S cerevisiae; D017346:Protein Serine-Threonine Kinases