Sequence, organization, and evolution of the A+T region of Drosophila melanogaster mitochondrial DNA.
The long (4.6-kb) A+T region of Drosophila melanogaster mitochondrial DNA has been cloned and sequenced. The A+T region is organized in two large arrays of tandemly repeated DNA sequence elements, with nonrepetitive intervening and flanking sequences comprising only 22% of its length. The first repeat array consists of five repeats of 338-373 bp. The second consists of four intact 464-bp repeats and a fifth partial repeat of 137 bp. Three DNA sequence elements are found to be highly conserved in D. melanogaster and in several Drosophila species with short A+T regions. These include a 300-bp DNA sequence element that overlaps the DNA replication origin and two thymidylate stretches identified on opposite DNA strands. We conclude that the length heterogeneity observed in the A+T regulatory region in mitochondrial DNAs from the genus Drosophila results from the expansion (and contraction) of the number of repeated DNA sequence elements. We also propose that the 300-bp conserved DNA sequence element, in conjunction with another primary sequence determinant, perhaps the adjacent thymidylate stretch, functions in the regulation of mitochondrial DNA replication.
Department of Biochemistry, Michigan State University, East Lansing 48824-1319.
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Lewis
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Farquhar
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Kaguni
D000818:Animals; D001482:Base Composition; D001483:Base Sequence; D005075:Biological Evolution; D003001:Cloning, Molecular; D017124:Conserved Sequence; D004272:DNA, Mitochondrial / Q000737:chemistry / Q000235:genetics*; D004331:Drosophila melanogaster / Q000235:genetics*; D008969:Molecular Sequence Data; D012091:Repetitive Sequences, Nucleic Acid; D015183:Restriction Mapping; D012689:Sequence Homology, Nucleic Acid
D004272:DNA, Mitochondrial