The 3' ends of most Saccharomyces cerevisiae mitochondrial mRNAs terminate at a conserved dodecamer sequence, 5'-AAUAAUAUUCUU-3', of unknown function. We have studied the consequences of mutations within a dodecamer found in an 1,143-base-pair optional intron of the mitochondrial large (21S) rRNA gene on RNA processing. The dodecamer is situated at the 3' end of an expressed open reading frame (ORF) within that intron, and the mutations are two adjacent transversions that extend the intron ORF by 51 nucleotides. The strain harboring these mutations, L5-10-1, is defective in biased intron transmission in crosses to strains that lack the intron, as are other mutants which contain nucleotide changes within the ORF (I. G. Macreadie, R. M. Scott, A. R. Zinn, and R. A. Butow, Cell 41:395-402, 1985). However, unlike these other mutants, wild-type strains, or petites which retain the intron allele, L5-10-1 is defective in processing at the intron dodecamer. In addition, L5-10-1 lacks a prominent 2.7-kilobase RNA containing both intron and exon sequences and at least two of four RNAs that correspond to various forms of the excised intron. We propose that these RNAs, missing in L5-10-1 but present in al other strains examined, arise in part by processing at the intron dodecamer. In addition, in all strains examined, we have detected a novel processing activity in which precursor 21S rRNA transcripts are cleaved in the upstream exon, about 1,500 nucleotides from the 5' end of the RNA. This activity, together with 3' intron dodecamer cleavage, probably accounts for the 2.7-kilobase RNA species, a candidate for the mRNA for the intron-encoded protein.Mature transcripts of the mitochondrial genome of Saccharomyces cerevisiae are generated by diverse pathways. Some genes contain a highly conserved nonanucleotide sequence at their 5' end that functions as an initiator for mitochondrial RNA polymerase (7,29). Other genes are cotranscribed into polycistronic precursors that are subsequently processed to yield the mature RNAs (6, 9, 23, 37). At the 3' end of almost all yeast mitochondrial protein structural genes is a highly conserved dodecamer sequence, 5'-AATAATATTCTT-3', which is located either between genes within a single transcription unit or at the 3' end of a transcription unit. In either case, the putative mRNAs for these genes terminate within the dodecamer sequence, most likely as a result of processing (30,33). The role of this 12-mer in mRNA activity or stability is unknown.A conserved dodecamer is also found within an optional 1,143-base-pair (bp) intron in the 21S rRNA gene but in an unusual location; it is at the 3' end of a freestanding open reading frame (ORF) (13) located entirely within the intron, and the termination codon for that ORF is part of the dodecamer sequence. The 21S rRNA intron is unique among optional mitochondrial introns, because in genetic crosses between strains that have it (wX) and those lacking it (w-), almost all of the w-alleles are converted to w+ (14,40 when crosses are carried out betw...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.