Translation of chloroplast psbD mRNA in Chlamydomonas is controlled by a secondary RNA structure blocking the AUG start codon.
Translation initiation represents a key step during regulation of gene expression in chloroplasts. Here, we report on the identification and characterization of three suppressor point mutations which overcome a translational defect caused by the deletion of a U-rich element in the 5'-untranslated region (5'-UTR) of the psbD mRNA in the green alga Chlamydomonas reinhardtii. All three suppressors affect a secondary RNA structure encompassing the psbD AUG initiation codon within a double-stranded region as judged by the analysis of site-directed chloroplast mutants as well as in vitro RNA mapping experiments using RNase H. In conclusion, the data suggest that these new element serves as a negative regulator which mediates a rapid shut-down of D2 synthesis.
Klinkert
Birgit
B
Allgemeine und Molekulare Botanik, Ruhr-Universität Bochum, Universitätsstr. 150, D-44780 Bochum, Germany.
Elles
Ingolf
I
Nickelsen
Jörg
J
D020121:5' Untranslated Regions / Q000737:chemistry* / Q000378:metabolism; D000818:Animals; D016825:Chlamydomonas reinhardtii / Q000235:genetics* / Q000378:metabolism; D002736:Chloroplasts / Q000235:genetics* / Q000378:metabolism; D018387:Codon, Initiator; D005786:Gene Expression Regulation; D009690:Nucleic Acid Conformation; D010442:Peptide Chain Initiation, Translational; D045332:Photosystem II Protein Complex / Q000096:biosynthesis / Q000235:genetics*; D017354:Point Mutation; D048030:RNA, Algal / Q000737:chemistry; D016601:RNA-Binding Proteins / Q000378:metabolism; D038621:Regulatory Sequences, Ribonucleic Acid; D013489:Suppression, Genetic; D014529:Uridine / Q000032:analysis
D020121:5' Untranslated Regions; D018387:Codon, Initiator; D045332:Photosystem II Protein Complex; D048030:RNA, Algal; D016601:RNA-Binding Proteins; D038621:Regulatory Sequences, Ribonucleic Acid; D014529:Uridine