title: Structural and functional insights into Saccharomyces cerevisiae Tpa1, a putative prolylhydroxylase influencing translation termination and transcription.
abstract: Efficiency of translation termination relies on the specific recognition of the three stop codons by the eukaryotic translation termination factor eRF1. To date only a few proteins are known to be involved in translation termination in eukaryotes. Saccharomyces cerevisiae Tpa1, a largely conserved but uncharacterized protein, has been described to associate with a messenger ribonucleoprotein complex located at the 3' end of mRNAs that contains at least eRF1, eRF3, and Pab1. Deletion of the TPA1 gene results in a decrease of translation termination efficacy and an increase in mRNAs half-lives and longer mRNA poly(A) tails. In parallel, Schizosaccharomyces pombe Ofd1, a Tpa1 ortholog, and its partner Nro1 have been implicated in the regulation of the stability of a transcription factor that regulates genes essential for the cell response to hypoxia. To gain insight into Tpa1/Ofd1 function, we have solved the crystal structure of S. cerevisiae Tpa1 protein. This protein is composed of two equivalent domains with the double-stranded β-helix fold. The N-terminal domain displays a highly conserved active site with strong similarities with prolyl-4-hydroxylases. Further functional studies show that the integrity of Tpa1 active site as well as the presence of Yor051c/Ett1 (the S. cerevisiae Nro1 ortholog) are essential for correct translation termination. In parallel, we show that Tpa1 represses the expression of genes regulated by Hap1, a transcription factor involved in the response to levels of heme and oxygen. Altogether, our results support that Tpa1 is a putative enzyme acting as an oxygen sensor and influencing several distinct regulatory pathways.
authors.affiliation: Institut de Biochimie et Biophysique Moléculaire et Cellulaire, CNRS UMR8619 Bat 430 Université Paris Sud, 91405 Orsay Cedex, France.
authors.forename: Julien
authors.initials: J
authors.lastname: Henri
authors.forename: Delphine
authors.initials: D
authors.lastname: Rispal
authors.forename: Emilie
authors.initials: E
authors.lastname: Bayart
authors.forename: Herman
authors.initials: H
authors.lastname: van Tilbeurgh
authors.forename: Bertrand
authors.initials: B
authors.lastname: Séraphin
authors.forename: Marc
authors.initials: M
authors.lastname: Graille
mesh_terms: D002352:Carrier Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal / Q000502:physiology; D006418:Heme / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D010100:Oxygen / Q000737:chemistry / Q000378:metabolism; D010443:Peptide Chain Termination, Translational / Q000502:physiology*; D011393:Procollagen-Proline Dioxygenase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D017510:Protein Folding; D017433:Protein Structure, Secondary; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D013329:Structure-Activity Relationship; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic / Q000502:physiology*
chemical_list: D002352:Carrier Proteins; D004268:DNA-Binding Proteins; C058452:HAP1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C548775:Tpa1 protein, S cerevisiae; D014157:Transcription Factors; D006418:Heme; D011393:Procollagen-Proline Dioxygenase; D010100:Oxygen