title: Dual functions of the nucleus-encoded factor TDA1 in trapping and translation activation of atpA transcripts in Chlamydomonas reinhardtii chloroplasts.
abstract: After endosymbiosis, organelles lost most of their initial genome. Moreover, expression of the few remaining genes became tightly controlled by the nucleus through trans-acting protein factors that are required for post-transcriptional expression (maturation/stability or translation) of a single (or a few) specific organelle target mRNA(s). Here, we characterize the nucleus-encoded TDA1 factor, which is specifically required for translation of the chloroplast atpA transcript that encodes subunit α of ATP synthase in Chlamydomonas reinhardtii. The sequence of TDA1 contains eight copies of a degenerate 38-residue motif, that we named octotrico peptide repeat (OPR), which has been previously described in a few other trans-acting factors targeted to the C. reinhardtii chloroplast. Interestingly, a proportion of the untranslated atpA transcripts are sequestered into high-density, non-polysomic, ribonucleoprotein complexes. Our results suggest that TDA1 has a dual function: (i) trapping a subset of untranslated atpA transcripts into non-polysomic complexes, and (ii) translational activation of these transcripts. We discuss these results in light of our previous observation that only a proportion of atpA transcripts are translated at any given time in the chloroplast of C. reinhardtii.
authors.affiliation: Unité Mixte de Recherche (UMR) 7141, Centre National de la Recherche Scientifique (CNRS) and Université Pierre et Marie Curie (UPMC - Paris 06), Institut de Biologie Physico-Chimique, 13 rue Pierre et Marie Curie, F-75005 Paris, France. Stephan.Eberhard@ibpc.fr
authors.forename: Stephan
authors.initials: S
authors.lastname: Eberhard
authors.forename: Christelle
authors.initials: C
authors.lastname: Loiselay
authors.forename: Dominique
authors.initials: D
authors.lastname: Drapier
authors.forename: Sandrine
authors.initials: S
authors.lastname: Bujaldon
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Girard-Bascou
authors.forename: Richard
authors.initials: R
authors.lastname: Kuras
authors.forename: Yves
authors.initials: Y
authors.lastname: Choquet
authors.forename: Francis-André
authors.initials: FA
authors.lastname: Wollman
mesh_terms: D020121:5' Untranslated Regions; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D002467:Cell Nucleus / Q000235:genetics; D016825:Chlamydomonas reinhardtii / Q000235:genetics / Q000378:metabolism*; D025222:Chloroplast Proton-Translocating ATPases / Q000235:genetics* / Q000378:metabolism; D002736:Chloroplasts / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D018506:Gene Expression Regulation, Plant; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism*; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000096:biosynthesis; D012261:Ribonucleoproteins / Q000378:metabolism
chemical_list: D020121:5' Untranslated Regions; D010940:Plant Proteins; D012333:RNA, Messenger; D012261:Ribonucleoproteins; D025222:Chloroplast Proton-Translocating ATPases