Loss of the mRNA-like region in mitochondrial tmRNAs of jakobids
Abstract
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 tRNAAla-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.
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Footnotes
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↵3 Present address: Department of Biology, Indiana University, 1001 E. Third St., Bloomington, IN 47405, USA.
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Article and publication are at http://www.rnajournal.org/cgi/doi/10.1261/rna.5227904.
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- Accepted December 29, 2003.
- Received November 10, 2003.
- Copyright 2004 by RNA Society