Comparison of fungal mitochondrial introns reveals extensive homologies in RNA secondary structure

Genomic Exploration of the Hemiascomycetous Yeasts: 10.Kluyveromyces thermotolerans

“…Despite the small mitochondrial genome size, we also identi¢ed a new putative mitochondrial group I intron open reading frame (ORF) whose closest homologue is I-SceII [16]. Until now, only one putative intronic meganuclease from K. thermotolerans had been identi¢ed by sequence similarity with I-SceI [8,9]. Finally, one RST contains a short segment which, upon translation, shows 92% amino acid identity with the C-terminal part of a hypothetical ORF 11 of S. cerevisiae.…”

Group I Ribozymes: Substrate Recognition, Catalytic Strategies, and Comparative Mechanistic Analysis

“…By 1985 the sequential steps in RNA selfsplicing had been described (Zaug and Cech 1982) and the secondary structure common to group I introns had been determined (Davies et al 1982;Michel et al 1982;Waring and Davies 1984). Furthermore, several fungal mitochondrial introns and one from bacteriophage T4 had joined the Tetrahymena rRNA intron on the list of self-splicers (Garriga and Lambowitz 1984;Chu et al 1985;van der Horst and Tabak 1985).…”

Thein vivouse of alternate 3′-splice sites in group I introns

“…Alternative splicing, as normal splicing of group I introns, would be guided in the splice site selection by secondary structures of the intron and achieved by its catalytic core (4). The selection of the 3'-splice site was shown, on the basis of sequence examinations (5,6) and in vitro experiments (7), to depend upon either one or both of two long distance pairings involving nucleotides immediately preceeding -P9-0- (8,9,10) and following -PlO- (6,11) (14). Sequence determination was carried out using the BRL Sequenase kit; primers were those previously used for PCR amplifications (Fig.…”

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ABSTRACT (5,6) and in vitro experiments (7), to depend upon either one or both of two long distance pairings involving nucleotides immediately preceeding -P9-0-(8, 9, 10) and following -PlO-(6, 11) the invariable G terminal nucleotide residue of the group I introns. The alternative selection of an internal 3'-splice site, concerning only a minority of the primary transcripts, would bring the discontinous ORF in frame with the upstream exon and thus ensure a low level translation of the intron encoded protein.

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