Yeast exonuclease 5 is essential for mitochondrial genome maintenance

Peter M. Burgers, Carrie M. Stith, Bonita L. Yoder, Justin L. Sparks

Research output: Contribution to journalArticlepeer-review

17 Scopus citations


Yeast exonuclease 5 is encoded by the YBR163w (DEM1) gene, and this gene has been renamed EXO5. It is distantly related to the Escherichia coli RecB exonuclease class. Exo5 is localized to the mitochondria, and EXO5 deletions or nuclease-defective EXO5 mutants invariably yield petites, amplifying either the ori3 or ori5 region of the mitochondrial genome. These petites remain unstable and undergo continuous rearrangement. The mitochondrial phenotype of exo5Δ strains suggests an essential role for the enzyme in DNA replication and recombination. No nuclear phenotype associated with EXO5 deletions has been detected. Exo5 is a monomeric 5′ exonuclease that releases dinucleotides as products. It is specific for single-stranded DNA and does not hydrolyze RNA. However, Exo5 has the capacity to slide across 5′ double-stranded DNA or 5′ RNA sequences and resumes cutting two nucleotides downstream of the double-stranded-to-single-stranded junction or RNA-to-DNA junction, respectively.

Original languageEnglish
Pages (from-to)1457-1466
Number of pages10
JournalMolecular and cellular biology
Issue number6
StatePublished - Mar 2010


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