The Glc7p nuclear phosphatase promotes mRNA export by facilitating association of Mex67p with mRNA.
mRNA export is mediated by Mex67p:Mtr2p/NXF1:p15, a conserved heterodimeric export receptor that is thought to bind mRNAs through the RNA binding adaptor protein Yra1p/REF. Recently, mammalian SR (serine/arginine-rich) proteins were shown to act as alternative adaptors for NXF1-dependent mRNA export. Npl3p is an SR-like protein required for mRNA export in S. cerevisiae. Like mammalian SR proteins, Npl3p is serine-phosphorylated by a cytoplasmic kinase. Here we report that this phosphorylation of Npl3p is required for efficient mRNA export. We further show that the mRNA-associated fraction of Npl3p is unphosphorylated, implying a subsequent nuclear dephosphorylation event. We present evidence that the essential, nuclear phosphatase Glc7p promotes dephosphorylation of Npl3p in vivo and that nuclear dephosphorylation of Npl3p is required for mRNA export. Specifically, recruitment of Mex67p to mRNA is Glc7p dependent. We propose a model whereby a cycle of cytoplasmic phosphorylation and nuclear dephosphorylation of shuttling SR adaptor proteins regulates Mex67p:Mtr2p/NXF1:p15-dependent mRNA export.
Gilbert
Wendy
W
Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, CA 94143, USA.
Guthrie
Christine
C
D001692:Biological Transport; D002467:Cell Nucleus / Q000378:metabolism*; D005822:Genetic Vectors; D017403:In Situ Hybridization; D008954:Models, Biological; D009687:Nuclear Proteins / Q000378:metabolism*; D029543:Nucleocytoplasmic Transport Proteins / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D010766:Phosphorylation; D011061:Poly A; D011485:Protein Binding; D054645:Protein Phosphatase 1; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D013696:Temperature; D014466:Ultraviolet Rays; D039221:mRNA Cleavage and Polyadenylation Factors / Q000378:metabolism
C106898:MEX67 protein, S cerevisiae; C077734:NPL3 protein, S cerevisiae; D009687:Nuclear Proteins; D029543:Nucleocytoplasmic Transport Proteins; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D029701:Saccharomyces cerevisiae Proteins; D039221:mRNA Cleavage and Polyadenylation Factors; D011061:Poly A; C092048:GLC7 protein, S cerevisiae; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1