In vitro processing of transcripts containing novel tRNA-like sequences ('t-elements') encoded by wheat mitochondrial DNA.
We have recently described the properties of a wheat mitochondrial extract that is able to process, accurately and efficiently, artificial transcripts containing wheat mitochondrial tRNA sequences, with the production of mature tRNAs (P.J. Hanic-Joyce and M.W. Gray, J. Biol. Chem., in press). Such processing involves 5'-endonucleolytic, 3'-endonucleolytic, and tRNA nucleotidyltransferase activities. Here we show that this system also acts on transcripts containing sequences corresponding to an unusual class of short repeats ('t-elements') in wheat mtDNA. These repeats are theoretically capable of assuming a tRNA-like secondary structure, although stable transcripts corresponding to them are not detectable in vivo. We find that t-element sequences are processed with the same specificity and with comparable efficiency as are authentic tRNA sequences. Because known t-elements are located close to and in the same transcriptional orientation as active genes (18S-5S, 26S, tRNA(Pro)) in wheat mtDNA, our results raise the question of whether t-elements play a role in gene expression in wheat mitochondria.
Hanic-Joyce
P J
PJ
Department of Biochemistry, Dalhousie University, Halifax, Nova Scotia, Canada.
Spencer
D F
DF
Gray
M W
MW
D001483:Base Sequence; D004247:DNA; D004272:DNA, Mitochondrial / Q000235:genetics*; D005786:Gene Expression Regulation; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D012322:RNA Precursors / Q000378:metabolism; D012323:RNA Processing, Post-Transcriptional; D012343:RNA, Transfer / Q000378:metabolism*; D012091:Repetitive Sequences, Nucleic Acid; D014158:Transcription, Genetic; D014908:Triticum / Q000235:genetics* / Q000648:ultrastructure
D004272:DNA, Mitochondrial; D012322:RNA Precursors; D004247:DNA; D012343:RNA, Transfer