Abstract
Introns are found in various tRNA genes in all the three kingdoms of life. Especially, archaeal and eukaryotic genomes are good sources of tRNA introns that are removed by proteinaceous splicing machinery. Most intron-containing tRNA genes both in archaea and eukaryotes possess an intron at a so-called canonical position, one nucleotide 3′ to their anticodon, while recent bioinformatics have revealed unusual types of tRNA introns and their derivatives especially in archaeal genomes. Gain and loss of tRNA introns during various stages of evolution are obvious both in archaea and eukaryotes from analyses of comparative genomics. The splicing of tRNA molecules has been studied extensively from biochemical and cell biological points of view, and such analyses of eukaryotic systems provided interesting findings in the past years. Here, I summarize recent progresses in the analyses of tRNA introns and the splicing process, and try to clarify new and old questions to be solved in the next stages.
Highlights
Tohru Yoshihisa*Most intron-containing tRNA genes both in archaea and eukaryotes possess an intron at a so-called canonical position, one nucleotide 3 to their anticodon, while recent bioinformatics have revealed unusual types of tRNA introns and their derivatives especially in archaeal genomes
Introns are found in various tRNA genes in all the three kingdoms of life
STRUCTURAL CHARACTERISTICS OF tRNA GENES HARBORING INTRONS Introns found in archaeal and eukaryotic tRNA genes are mostly inserted at one nucleotide 3 to the anticodon, namely position 37/38 in the standard nomenclature (Figure 1) while introns are inserted into other parts of tRNA genes in minor cases
Summary
Most intron-containing tRNA genes both in archaea and eukaryotes possess an intron at a so-called canonical position, one nucleotide 3 to their anticodon, while recent bioinformatics have revealed unusual types of tRNA introns and their derivatives especially in archaeal genomes. Recent powerful sequence analyses with the generation sequencers accumulate an enormous amount of sequence information in tRNA genes through whole genome sequencing of non-model organisms from various evolutional clades and through metagenome analyses mostly of prokaryotic species. Their relatives, eukaryotic organellar genomes, small numbers of tRNA genes harbor the group I intron within the anticodon region (Reinhold-Hurek and Shub, 1992; Haugen et al, 2005) These introns are spliced by a series of phosphoester transfer reactions catalyzed by intronic sequences, whose mechanism is somehow related to splicing of mRNA. Length of introns ranges from 11 to 129 nt, and its median for each isodecoder www.frontiersin.org
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