title: Yeast poly(A)-binding protein Pab1 shuttles between the nucleus and the cytoplasm and functions in mRNA export.
abstract: Pab1 is the major poly(A)-binding protein in yeast. It is a multifunctional protein that mediates many cellular functions associated with the 3'-poly(A)-tail of messenger RNAs. Here, we characterize Pab1 as an export cargo of the protein export factor Xpo1/Crm1. Pab1 is a major Xpo1/Crm1-interacting protein in yeast extracts and binds directly to Xpo1/Crm1 in a RanGTP-dependent manner. Pab1 shuttles rapidly between the nucleus and the cytoplasm and partially accumulates in the nucleus when the function of Xpo1/Crm1 is inhibited. However, Pab1 can also be exported by an alternative pathway, which is dependent on the MEX67-mRNA export pathway. Import of Pab1 is mediated by the import receptor Kap108/Sxm1 through a nuclear localization signal in its fourth RNA-binding domain. Interestingly, inhibition of Pab1's nuclear import causes a kinetic delay in the export of mRNA. Furthermore, the inviability of a pab1 deletion strain is suppressed by a mutation in the 5'-3' exoribonuclease RRP6, a component of the nuclear exosome. Therefore, nuclear Pab1 may be required for efficient mRNA export and may function in the quality control of mRNA in the nucleus.
authors.affiliation: Department of Molecular and Cell Biology, Division of Cell and Developmental Biology, University of California, Berkeley, Berkeley, CA 94720-3200, USA.
authors.forename: Christiane
authors.initials: C
authors.lastname: Brune
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Munchel
authors.forename: Nicole
authors.initials: N
authors.lastname: Fischer
authors.forename: Alexandre V
authors.initials: AV
authors.lastname: Podtelejnikov
authors.forename: Karsten
authors.initials: K
authors.lastname: Weis
mesh_terms: D021581:Active Transport, Cell Nucleus; D002467:Cell Nucleus / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism*; D028884:Karyopherins / Q000378:metabolism; D009687:Nuclear Proteins / Q000378:metabolism; D029543:Nucleocytoplasmic Transport Proteins / Q000378:metabolism; D039122:Poly(A)-Binding Protein I / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D012331:RNA, Fungal / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism; D015003:Yeasts / Q000235:genetics / Q000378:metabolism*; D000097606:Exportin 1 Protein
chemical_list: D028884:Karyopherins; D009687:Nuclear Proteins; D029543:Nucleocytoplasmic Transport Proteins; D039122:Poly(A)-Binding Protein I; D012331:RNA, Fungal; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D018160:Receptors, Cytoplasmic and Nuclear; D029701:Saccharomyces cerevisiae Proteins; D000097606:Exportin 1 Protein; C106898:MEX67 protein, S cerevisiae; C110035:SXM1 protein, S cerevisiae