Loss of the mRNA-like region in mitochondrial tmRNAs of jakobids.
It has been postulated that a highly reduced form of transfer messenger RNA (tmRNA), a bacterial molecule involved in the rescue of stalled ribosomes during translation, is expressed in the mitochondrion of the jakobid Reclinomonas americana. Here we show that genes encoding both one-piece and two-piece tmRNAs are present in six different jakobid mitochondrial DNAs. Mitochondrial tmRNAs have retained the highly conserved tRNA(Ala)-like domain, but they apparently lack the mRNA-like region present in all bacterial tmRNAs. Comparative analysis of jakobid mitochondrial genomes shows that a potential mRNA-like region in R. americana (orf64) is located at distant genomic positions in other jakobids. Our results strongly suggest that orf64 is a tatA homolog. Through Northern hybridization we confirm the postulated reduced size of both a one-piece tmRNA in Jakoba libera and a two-piece tmRNA in Seculamonas ecuadoriensis. The J. libera tmRNA is post-transcriptionally modified by addition of a 3' CCA tail, processed in vitro by RNase P RNA, and specifically charged with alanine in vitro by alanyl-tRNA synthetase. Our results strongly support the functionality of these reduced mitochondrial tmRNAs.
Jacob
Yannick
Y
Département de Biochimie, Université de Montréal, Montréal, Québec, Canada H3T 1J4.
Seif
Elias
E
Paquet
Pierre-Olivier
PO
Lang
B Franz
BF
D000409:Alanine / Q000378:metabolism; D000818:Animals; D017124:Conserved Sequence; D004272:DNA, Mitochondrial / Q000235:genetics* / Q000378:metabolism; D056890:Eukaryota / Q000235:genetics* / Q000378:metabolism; D012322:RNA Precursors / Q000378:metabolism; D012323:RNA Processing, Post-Transcriptional; D012329:RNA, Bacterial / Q000378:metabolism*; D017422:Sequence Analysis, DNA
D004272:DNA, Mitochondrial; D012322:RNA Precursors; D012329:RNA, Bacterial; C096222:tmRNA; D000409:Alanine