The Shine-Dalgarno-like sequence is a negative regulatory element for translation of tobacco chloroplast rps2 mRNA: an additional mechanism for translational control in chloroplasts.
Most prokaryotic mRNAs contain within the 5' untranslated region (UTR), a Shine-Dalgarno (SD) sequence, which is complementary to the 3' end of 16S rRNA and serves as a major determinant for correct translational initiation. The tobacco chloroplast rps2 mRNA possesses an SD-like sequence (GGAG) at a proper position (positions -8 to -5 from the start codon). Using an in vitro translation system from isolated tobacco chloroplasts, the role of this sequence in translation was examined. Unexpectedly, the mutation of the SD-like element resulted in a large increase in translation. Internal and external deletions within the 5' UTR revealed that the region from -20 to -5 was involved in the negative regulation of translation. Scanning mutagenesis assays confirmed the above result. Competition assays suggested the existence of a trans-acting factor(s) involved in translational regulation. In this study, we discuss a possible mechanism for the negative regulation of rps2 mRNA translation.
Plader
Wojciech
W
Center for Gene Research, Nagoya University, Japan.
Sugiura
Masahiro
M
D020121:5' Untranslated Regions / Q000235:genetics; D001483:Base Sequence; D008969:Molecular Sequence Data; D014176:Protein Biosynthesis / Q000235:genetics*; D018747:RNA, Chloroplast / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics* / Q000378:metabolism; D012269:Ribosomal Proteins / Q000235:genetics*; D017384:Sequence Deletion / Q000235:genetics; D012689:Sequence Homology, Nucleic Acid; D014026:Nicotiana / Q000235:genetics*
D020121:5' Untranslated Regions; D018747:RNA, Chloroplast; D012333:RNA, Messenger; D012269:Ribosomal Proteins; C030004:ribosomal protein S2