title: Yeast shuttling SR proteins Npl3p, Gbp2p, and Hrb1p are part of the translating mRNPs, and Npl3p can function as a translational repressor.
abstract: A major challenge in current molecular biology is to understand how sequential steps in gene expression are coupled. Recently, much attention has been focused on the linkage of transcription, processing, and mRNA export. Here we describe the cytoplasmic rearrangement for shuttling mRNA binding proteins in Saccharomyces cerevisiae during translation. While the bulk of Hrp1p, Nab2p, or Mex67p is not associated with polysome containing mRNAs, significant amounts of the serine/arginine (SR)-type shuttling mRNA binding proteins Npl3p, Gbp2p, and Hrb1p remain associated with the mRNA-protein complex during translation. Interestingly, a prolonged association of Npl3p with polysome containing mRNAs results in translational defects, indicating that Npl3p can function as a negative translational regulator. Consistent with this idea, a mutation in NPL3 that slows down translation suppresses growth defects caused by the presence of translation inhibitors or a mutation in eIF5A. Moreover, using sucrose density gradient analysis, we provide evidence that the import receptor Mtr10p, but not the SR protein kinase Sky1p, is involved in the timely regulated release of Npl3p from polysome-associated mRNAs. Together, these data shed light onto the transformation of an exporting to a translating mRNP.
authors.affiliation: Institut für Molekularbiologie und Tumorforschung der Philipps-Universität Marburg, Emil-Mannkopff-Str. 2, 35037 Marburg, Germany.
authors.forename: Merle
authors.initials: M
authors.lastname: Windgassen
authors.forename: Dorothée
authors.initials: D
authors.lastname: Sturm
authors.forename: Iván J
authors.initials: IJ
authors.lastname: Cajigas
authors.forename: Carlos I
authors.initials: CI
authors.lastname: González
authors.forename: Matthias
authors.initials: M
authors.lastname: Seedorf
authors.forename: Holger
authors.initials: H
authors.lastname: Bastians
authors.forename: Heike
authors.initials: H
authors.lastname: Krebber
mesh_terms: D001692:Biological Transport; D015152:Blotting, Northern; D002499:Centrifugation, Density Gradient; D018389:Codon, Nonsense; D003513:Cycloheximide / Q000494:pharmacology; D003593:Cytoplasm / Q000378:metabolism; D017353:Gene Deletion; D049452:Green Fluorescent Proteins / Q000378:metabolism; D034441:Heterogeneous-Nuclear Ribonucleoproteins / Q000502:physiology*; D008856:Microscopy, Fluorescence; D009154:Mutation; D009687:Nuclear Proteins / Q000502:physiology*; D009693:Nucleic Acid Hybridization; D029543:Nucleocytoplasmic Transport Proteins / Q000737:chemistry*; D010957:Plasmids / Q000378:metabolism; D011061:Poly A / Q000737:chemistry; D039102:Poly(A)-Binding Proteins; D011132:Polyribosomes / Q000737:chemistry; D014176:Protein Biosynthesis; D017346:Protein Serine-Threonine Kinases / Q000502:physiology; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D012313:RNA / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D012335:RNA, Ribosomal / Q000737:chemistry / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012270:Ribosomes / Q000737:chemistry; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000502:physiology*; D013395:Sucrose / Q000494:pharmacology; D013696:Temperature; D013997:Time Factors; D014158:Transcription, Genetic
chemical_list: D018389:Codon, Nonsense; C474034:Gbp2 protein, S cerevisiae; D034441:Heterogeneous-Nuclear Ribonucleoproteins; C089362:Hrb1 protein, S cerevisiae; C110033:MTR10 protein, S cerevisiae; C077734:NPL3 protein, S cerevisiae; D009687:Nuclear Proteins; D029543:Nucleocytoplasmic Transport Proteins; D039102:Poly(A)-Binding Proteins; D011500:Protein Synthesis Inhibitors; D012333:RNA, Messenger; D012335:RNA, Ribosomal; D016601:RNA-Binding Proteins; D029701:Saccharomyces cerevisiae Proteins; D049452:Green Fluorescent Proteins; D011061:Poly A; D013395:Sucrose; D012313:RNA; D003513:Cycloheximide; C490216:SKY1 protein, S cerevisiae; D017346:Protein Serine-Threonine Kinases