title: Pub1p C-terminal RRM domain interacts with Tif4631p through a conserved region neighbouring the Pab1p binding site.
abstract: Pub1p, a highly abundant poly(A)+ mRNA binding protein in Saccharomyces cerevisiae, influences the stability and translational control of many cellular transcripts, particularly under some types of environmental stresses. We have studied the structure, RNA and protein recognition modes of different Pub1p constructs by NMR spectroscopy. The structure of the C-terminal RRM domain (RRM3) shows a non-canonical N-terminal helix that packs against the canonical RRM fold in an original fashion. This structural trait is conserved in Pub1p metazoan homologues, the TIA-1 family, defining a new class of RRM-type domains that we propose to name TRRM (TIA-1 C-terminal domain-like RRM). Pub1p TRRM and the N-terminal RRM1-RRM2 tandem bind RNA with high selectivity for U-rich sequences, with TRRM showing additional preference for UA-rich ones. RNA-mediated chemical shift changes map to β-sheet and protein loops in the three RRMs. Additionally, NMR titration and biochemical in vitro cross-linking experiments determined that Pub1p TRRM interacts specifically with the N-terminal region (1-402) of yeast eIF4G1 (Tif4631p), very likely through the conserved Box1, a short sequence motif neighbouring the Pab1p binding site in Tif4631p. The interaction involves conserved residues of Pub1p TRRM, which define a protein interface that mirrors the Pab1p-Tif4631p binding mode. Neither protein nor RNA recognition involves the novel N-terminal helix, whose functional role remains unclear. By integrating these new results with the current knowledge about Pub1p, we proposed different mechanisms of Pub1p recruitment to the mRNPs and Pub1p-mediated mRNA stabilization in which the Pub1p/Tif4631p interaction would play an important role.
authors.affiliation: Department of Biological Physical Chemistry, Instituto de Química-Física Rocasolano, CSIC, Madrid, Spain.
authors.forename: Clara M
authors.initials: CM
authors.lastname: Santiveri
authors.forename: Yasmina
authors.initials: Y
authors.lastname: Mirassou
authors.forename: Palma
authors.initials: P
authors.lastname: Rico-Lastres
authors.forename: Santiago
authors.initials: S
authors.lastname: Martínez-Lumbreras
authors.forename: José Manuel
authors.initials: JM
authors.lastname: Pérez-Cañadillas
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D019731:Carbon-Nitrogen Ligases / Q000737:chemistry*; D039603:Eukaryotic Initiation Factor-4G / Q000737:chemistry*; D005656:Fungal Proteins / Q000737:chemistry; D015966:Gene Expression Regulation, Fungal; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D014176:Protein Biosynthesis; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry*; D029702:Schizosaccharomyces pombe Proteins / Q000737:chemistry*; D017386:Sequence Homology, Amino Acid; D012995:Solubility
chemical_list: D039603:Eukaryotic Initiation Factor-4G; D005656:Fungal Proteins; D029701:Saccharomyces cerevisiae Proteins; D029702:Schizosaccharomyces pombe Proteins; C107740:TIF4631 protein, S cerevisiae; D019731:Carbon-Nitrogen Ligases; C098922:Pub1 protein, S pombe