The complete sequence of the 16,569-base pair human mitochondrial genome is presented. The genes for the 12S and 16S rRNAs, 22 tRNAs, cytochrome c oxidase subunits I, II and III, ATPase subunit 6, cytochrome b and eight other predicted protein coding genes have been located. The sequence shows extreme economy in that the genes have none or only a few noncoding bases between them, and in many cases the termination codons are not coded in the DNA but are created post-transcriptionally by polyadenylation of the mRNAs.

Sequence and organization of the human mitochondrial genome

THE MITOCHONDRIAL GENETIC SYSTEM ....•••••• ••••••••••.• ••••••••••..•......... 291 Organization and Expression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... . . . . . . . . . . 291 Genetic Content 296 Regulation of Mitochondrial Gene Expression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 300

Biogenesis of Mitochondria

Recent evidence for evolution of the genetic code.

Comparison of the human mitochrondrial DNA sequence of the cytochrome oxidase subunit II gene and the sequence of the corresponding beef heart protein shows that UGA is used as a tryptophan codon and not as a termination codon and suggests that AU A may be a methionine and not an isoleucine codon. The cytochrome oxidase II gene is contiguous at its 5′ end with a tRNAAsp gene and there are only 25 bases at its 3′ end before a tRNALys gene. These tRNAs are different from all other known tRNA sequences.

A different genetic code in human mitochondria

https://mmbr.asm.org/content/mmbr/46/1/1.full.pdf

Has the endosymbiont hypothesis been proven

We have determined the nucleotide sequence of a segment of Saccharomyces mtDNA that contains the structural gene for one of the subunits (the dicyclohexylcarbodiimide-binding protein) of the mitochondrial ATPase complex. The sequence fits the known amino acid sequence of this protein with the exception of one amino acid. Codon usage is biased in favor of A + T-rich codons. On both sides of the gene, the nucleotide sequence contains less than 4% (mol/mol) G + C for at least 180 nucleotides; these A + T sequences show no evidence of internal repetition. The gene and all the A + T-rich sequence preceding the gene are present in a 12S RNA that is the major transcript of this segment of mtDNA. The nature of the sequences responsible for binding ribosomes to mitochondrial mRNA and for termination of RNA synthesis is considered.

Nucleotide sequence of the mitochondrial structural gene for subunit 9 of yeast ATPase complex.

Wehavedetermined thenucleotide sequence ofasegment ofSaccharomyces mtDNAthat contains the structural geneforoneofthesubunits (the dicyclohexylcarbo- diimide-binding protein) ofthemitochondrial ATPasecomplex. Thesequence fits theknown amino acid sequence ofthis protein withtheexception ofoneaminoacid. Codonusage isbiased in favor ofA+T-rich codons. Onbothsides ofthegene, thenu- cleotide sequence contains less than 4%(mol/mol) G+Cfor at least 180nucleotides; these A+Tsequences shownoevidence ofinternal repetition. Thegeneandall theA+T-rich sequence preceding thegenearepresent ina12SRNAthat isthemajor transcript, ofthis segment ofmtDNA.Thenature ofthese- quences responsible forbinding ribosomes tomitochondrial mRNAandfortermination ofRNAsynthesis isconsidered. ThemtDNAoftheyeast Saccharomyces isa25-,rm circle (1), which contains genes for rRNAs, tRNAs, andalimited number ofproteins (see Fig. 1). Biochemical analysis ofthis DNAand its transcripts hasuncovered several interesting features (see ref. 7for review). TheDNAcontains only 18%(mol/mol) G+C (8), andabout half ofitismadeupofsegments that arenearly pure A+T(9). Intervening sequences have been found both in thegenefor thelarge rRNA(10) andinthestructural gene for apocytochrome b(7, 11,12), andinboth cases these intervening sequences have beenshown tovary insize inclosely related Saccharomyces strains (7). Tounderstand thebiological significance ofthese features ofyeast mtDNA,detailed information onstrategic sequences inthis DNAisindispensable. Asuitable starting point forse- quence analysis ofprotein-specifying genes istheolil locus. This locus isknown tocode forsubunit 9(the so-called dicy- clohexylcarbodiimide-binding protein) ofthemitochondrial ATPase complex, andtheamino acid sequence ofthis protein isknown(13). Mutations atthis locus maylead tooligomycin resistance ofmitochondrial ATPase, andamino acid substitu- tions corresponding tothese mutations have been determined (13, 14). Slonimski andcoworkers have isolated thepetite mutant RP6, which cantransmit oligomycin resistance ingenetic crosses (15) andwhich contains asingle amplified 1025-base pair fragment ofwild-type mtDNA.This DNAhasbeen used tomaptheolil locus ontherestriction fragment mapofmtDNA(15), andwe have nowused RP6asaconvenient source ofpurified DNAto determine thenucleotide sequence ofthestructural genefor ATPase subunit 9andthesequences surrounding this gene. MATERIALSAND METHODS Yeast Strains andIsolation ofmtDNA.Thewild-type strain ofSaccharomyces cerevisiae KL14-4A wasobtained fromR. J.Schweyen, Genetisches Institut, MunichUniversity, West Germany. Petite mutant RP6wasobtained fromP.P.Slo- nimski, Centre deGenetique Moleculaire duCentre National delaRecherche Scientifique (Gif-sur-Yvette, France). Reten- tion oftheolil marker inthis petite waschecked bytherep- lica-cross technique ofDeutsch etal. (16) andfound tobe>99%

Nucleotide sequence ofthemitochondrial structural genefor subunit 9ofyeast ATPasecomplex (petite mutantDNA/dideoxy sequence method/A+T-rich sequences/codon usage/mtDNA)

Lambertus A. M. Hensgens

Papers

Nucleotide sequence of the mitochondrial structural gene for subunit 9 of yeast ATPase complex.

Nucleotide sequence ofthemitochondrial structural genefor subunit 9ofyeast ATPasecomplex (petite mutantDNA/dideoxy sequence method/A+T-rich sequences/codon usage/mtDNA)