title: Arginine methylation of the nuclear poly(a) binding protein weakens the interaction with its nuclear import receptor, transportin.
abstract: The nuclear poly(A) binding protein, PABPN1, promotes mRNA polyadenylation in the cell nucleus by increasing the processivity of poly(A) polymerase and contributing to poly(A) tail length control. In its C-terminal domain, the protein carries 13 arginine residues that are all asymmetrically dimethylated. The function of this modification in PABPN1 has been unknown. Part of the methylated domain serves as nuclear localization signal, binding the import receptor transportin. Here we report that arginine methylation weakens the affinity of PABPN1 for transportin. Recombinant, unmethylated PABPN1 binds more strongly to transportin than its methylated counterpart from mammalian tissue, and in vitro methylation reduces the affinity. Transportin and RNA compete for binding to PABPN1. Methylation favors RNA binding. Transportin also inhibits in vitro methylation of the protein. Finally, a peptide corresponding to the nuclear localization signal of PABPN1 competes with transportin-dependent nuclear import of the protein in a permeabilized cell assay and does so less efficiently when it is methylated. We hypothesize that transportin binding might delay methylation of PABPN1 until after nuclear import. In the nucleus, arginine methylation may favor the transition of PABPN1 to the competing ligand RNA and serve to reduce the risk of the protein being reexported to the cytoplasm by transportin.
authors.affiliation: Institute of Biochemistry and Biotechnology, Martin Luther University Halle-Wittenberg, 06099 Halle, Germany.
authors.forename: Katharina
authors.initials: K
authors.lastname: Fronz
authors.forename: Stefan
authors.initials: S
authors.lastname: Güttinger
authors.forename: Kerstin
authors.initials: K
authors.lastname: Burkert
authors.forename: Uwe
authors.initials: U
authors.lastname: Kühn
authors.forename: Nadine
authors.initials: N
authors.lastname: Stöhr
authors.forename: Angelika
authors.initials: A
authors.lastname: Schierhorn
authors.forename: Elmar
authors.initials: E
authors.lastname: Wahle
mesh_terms: D021581:Active Transport, Cell Nucleus; D000595:Amino Acid Sequence; D000818:Animals; D001120:Arginine / Q000378:metabolism*; D001667:Binding, Competitive; D002417:Cattle; D002467:Cell Nucleus / Q000378:metabolism*; D055786:Gene Knockout Techniques; D006367:HeLa Cells; D006801:Humans; D028884:Karyopherins / Q000378:metabolism*; D008745:Methylation; D008969:Molecular Sequence Data; D019913:Nuclear Localization Signals / Q000378:metabolism; D039103:Poly(A)-Binding Protein II / Q000737:chemistry / Q000378:metabolism*; D039102:Poly(A)-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D011484:Protein-Arginine N-Methyltransferases / Q000378:metabolism; D012313:RNA / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism
chemical_list: D028884:Karyopherins; D019913:Nuclear Localization Signals; D039103:Poly(A)-Binding Protein II; D039102:Poly(A)-Binding Proteins; D018160:Receptors, Cytoplasmic and Nuclear; D011994:Recombinant Proteins; D012313:RNA; D001120:Arginine; D011484:Protein-Arginine N-Methyltransferases