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Mol. Cell. Biol., 09 1995, 4803-4809, Vol 15, No. 9
HE Lorimer, BJ Brewer and WL Fangman
Two strand-specific origins of replication appear to be required for
mammalian mitochondrial DNA (mtDNA) replication. Structural equivalents of
these origins are found in the rep sequences of Saccharomyces cerevisiae
mtDNA. These striking similarities have contributed to a universal model
for the initiation of mtDNA replication in which a primer is created by
cleavage of an origin region transcript. Consistent with this model are the
properties of deletion mutants of yeast mtDNA ([rho-]) with a high density
of reps (HS [rho-]). These mutant mtDNAs are preferentially inherited by
the progeny resulting from the mating of HS [rho-] cells with cells
containing wild-type mtDNA ([rho+]). This bias is presumed to result from a
replication advantage conferred on HS [rho-] mtDNA by the high density of
rep sequences acting as origins. To test whether transcription is indeed
required for the preferential inheritance of HS [rho-] mtDNA, we deleted
the nuclear gene (RPO41) for the mitochondrial RNA polymerase, reducing
transcripts by at least 1000-fold. Since [rho-] genomes, but not [rho+]
genomes, are stable when RPO41 is deleted, we examined matings between HS
[rho-] and neutral [rho-] cells. Neutral [rho-] mtDNAs lack rep sequences
and are not preferentially inherited in [rho- ] x [rho+] crosses. In HS
[rho-] x neutral [rho-] matings, the HS [rho- ] mtDNA was preferentially
inherited whether both parents were wild type or both were deleted for
RPO41. Thus, transcription from the rep promoter does not appear to be
necessary for biased inheritance.(ABSTRACT TRUNCATED AT 250 WORDS)
Copyright © 1995, American Society for Microbiology
A test of the transcription model for biased inheritance of yeast mitochondrial DNA
Department of Genetics, University of Washington, Seattle 98195-7360, USA.
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