A petite mitochondrial DNA segment arising in exceptionally high frequency in a mit− mutant of Saccharomyces cerevisiae

Bingham, Christopher G.; Nagley, Phillip

doi:10.1016/0167-4781(83)90125-2

Cited by 18 publications

(6 citation statements)

References 19 publications

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“…The cob intron 4 (b14) mutation PZ16 is a typical 'box7' mutation that blocks the splicing of b14 and coxl intron 4a (aI4a) (8,9). It is a -1 frameshift that truncates the maturase reading frame so that a non-functional, roughly 14 kd, fragment of the b14 maturase accumulates. When cells of a haploid strain containing that mutation are plated on rich glucose medium, large colonies containing no obvious revertants are evident after three days incubation.…”

Section: Initial Observationsmentioning

confidence: 99%

Novel hybrid maturases in unstable pseudorevertants of maturaseless mutants of yeast mitochondrial DNA

et al. 1990

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Unstable pseudorevertants of mitochondrial mutants of Saccharomyces cerevisiae lacking the maturase function encoded by the fourth intron of the cytochrome b gene (bI4) were isolated. They were found to be heteroplasmic cells owing their regained ability to respire (and grow on glycerol medium) to the presence of a rearranged (rho-) mtDNA that contains an in-frame fusion of the reading frames of the group I introns bI4 and intron 4 alpha of the coxl gene encoding subunit I of cytochrome c oxidase (aI4 alpha). The products of those gene fusions suppress the bI4 maturase deficiency still present in those heteroplasmic cells. Similar heteroplasmic pseudorevertants of a group II maturaseless mutant of the first intron of the coxI gene were characterized; they result from partial deletion of the coxI gene that fuses the reading frames of introns 1 and 2. These heteroplasms provide independent support for the existence of RNA maturases encoded by group I and group II introns. Also, since the petite/mit- heteroplasms arise spontaneously at very high frequencies they provide a system that can be used to obtain mutants unable to form or maintain heteroplasmic cells.

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Section: Initial Observationsmentioning

confidence: 99%

Novel hybrid maturases in unstable pseudorevertants of maturaseless mutants of yeast mitochondrial DNA

et al. 1990

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“…Second, a systematic examination of GC clusters and their flanking DNA regions indicates that unique target sites exist for the various classes of GC clusters and that nucleotide duplications at these sites are a likely consequence of GC cluster insertion (16). This latter property of target sequence duplication is a characteristic feature of the transposition of most mobile genetic elements (17)(18)(19)(20) (22).Restriction Digestions, Transfers, and Hybridizations. All methods were performed as described (7) with the following tTo whom reprint requests should be addressed.…”

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confidence: 99%

“…This latter property of target sequence duplication is a characteristic feature of the transposition of most mobile genetic elements (17)(18)(19)(20) (21). mtDNAs were prepared by the method of Bingham and Nagley (22).…”

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confidence: 99%

In vivo double-strand breaks occur at recombinogenic G + C-rich sequences in the yeast mitochondrial genome.

Zinn

Pohlman

Perlman

et al. 1988

Proc. Natl. Acad. Sci. U.S.A.

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An optional 46-base-pair G+C-rich element (GC cluster) in the coding region of the yeast mitochondrial varl gene inserts preferentially in crosses into recipient alleles that lack the sequence. Unlike a similar gene conversion event involving the insertion of an optional 1143-base-pair intron, the mitochondrial 21S rRNA gene, which requires the action of a protein encoded by a gene within that intron, conversion of the var) GC cluster does not require any protein product of the mitochondrial genome. We have detected double-strand breaks in the varl gene in mitochondrial DNA isolated from unmated haploid p+ and p-strains at or near the boundaries of the optional GC cluster, as well as at a conserved copy of that sequence 160 base pairs upstream. No double-strand breaks were detected in the recipient varl DNA molecules in the vicinity of the optional GC cluster target sequence. This contrasts with 21S rRNA-encoding DNA (rDNA) intron conversion where the recipient, but not the donor DNA, is cleaved at the element insertion site. These results suggest that although the 21S rDNA intron and the var) GC duster are preferentially inserted into their respective short alleles, these conversions probably occur by different mechanisms.The -80-kilobase (kb) mitochondrial genome of Saccharomyces cerevisiae contains two distinct classes of optional DNA sequences. One class is evident among yeast strains as a variable number of introns located within the genes encoding cytochrome b, cytochrome oxidase subunit I, and the large (21S) rRNA (1); the other class is made up of a large number (>150) of G+C-rich sequences, called GC clusters, most of which are 30-60 base pairs (bp) long and are found dispersed throughout the yeast mitochondrial genome, mostly in the intergenic spaces (2-4). These GC clusters have been subdivided into various groups based on primary sequence homologies (4), and except for those few GC clusters located within the coding sequences of genes, their functions are unknown.For two particular optional mtDNA sequences, specialized recombination is evident in which an allele lacking that sequence acquires it in crosses by unidirectional gene conversion (5). One such recombination involves an optional 1143-bp intron, called co, located within the 21S rRNA gene.In crosses between wt and w-strains, nearly all of the calleles are converted to w+ (6, 7). The mechanism of this recombination event is now partly understood and closely resembles mating type interconversion in yeast nuclear DNA (8). Intron insertion is mediated in part by a protein, called fiti, encoded entirely within the 1143-bp intron (9, 10).That protein is a sequence-specific endonuclease that catalyzes a double-strand break in the DNA of the w-allele at the site of intron insertion (11); conversion probably occurs as a result of the replicative repair of the double-strand break in which the DNA of the a+ allele is used as a template (6-9). This conversion event thus has a clear dependence on mitochondrial protein synthesis.The other specializ...

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“…Mitochondrial DNA was isolated as previously described (17). The cloning of mtDNA fragments into phage M13 vectors and determination of nucleotide sequences by the dideoxy chain-termination method were carried out by standard procedures (18,19).…”

Section: Isolation Of Mtdna and Dna Sequence Determinationmentioning

confidence: 99%

A mitochondrial intergenic mutation affecting processing of specific yeast mitochondrial transcripts

Smooker¹,

Wright²,

Linnane³

et al. 1988

Nucl Acids Res

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The mutation in the temperature-conditional mit- mutant h56, mapped previously to the var1 gene region of Saccharomyces cerevisiae mitochondrial DNA, results in a specific inhibition of var1 protein synthesis in cells incubated at the non-permissive temperature, 36 degrees C (1). We have now characterized the mutation present in mutant h56 by DNA sequencing and found it to be an A to T transversion located 109 nucleotides upstream of the var1 reading frame. Two spontaneous revertants of mutant h56 restore the parental strain sequence at residue -109, confirming that this single base change within the 5'-untranslated region of the var1 mRNA is responsible for defective synthesis of the var1 protein. A comparison of var1 transcripts in the parental and mutant strains has shown that the mutation specifically blocks formation of var1 mRNA at 36 degrees C and leads to accumulation of precursor transcripts. Expression of the oli1 gene, co-transcribed with the var1 gene in primary transcripts, is not affected. It is concluded that the mutation in mutant h56 alters the secondary structure of the precursor RNA, inhibiting an endonucleolytic cleavage required to generate the 5' end of var1 mRNA.

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A petite mitochondrial DNA segment arising in exceptionally high frequency in a mit− mutant of Saccharomyces cerevisiae

Cited by 18 publications

References 19 publications

Novel hybrid maturases in unstable pseudorevertants of maturaseless mutants of yeast mitochondrial DNA

Novel hybrid maturases in unstable pseudorevertants of maturaseless mutants of yeast mitochondrial DNA

In vivo double-strand breaks occur at recombinogenic G + C-rich sequences in the yeast mitochondrial genome.

A mitochondrial intergenic mutation affecting processing of specific yeast mitochondrial transcripts

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