title: Yeast exonuclease 5 is essential for mitochondrial genome maintenance.
abstract: 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 exo5Delta 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.
authors.affiliation: Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St Louis, MO 63110, USA. burgers@biochem.wustl.edu
authors.forename: Peter M
authors.initials: PM
authors.lastname: Burgers
authors.forename: Carrie M
authors.initials: CM
authors.lastname: Stith
authors.forename: Bonita L
authors.initials: BL
authors.lastname: Yoder
authors.forename: Justin L
authors.initials: JL
authors.lastname: Sparks
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D002467:Cell Nucleus / Q000378:metabolism; D003001:Cloning, Molecular; D004249:DNA Damage; D004252:DNA Mutational Analysis; D004271:DNA, Fungal / Q000378:metabolism; D004272:DNA, Mitochondrial / Q000378:metabolism; D005092:Exonucleases / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D017353:Gene Deletion; D005800:Genes, Fungal / Q000235:genetics; D054629:Genome, Mitochondrial / Q000235:genetics*; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000302:isolation & purification; D010641:Phenotype; D012331:RNA, Fungal / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D004271:DNA, Fungal; D004272:DNA, Mitochondrial; D050505:Mutant Proteins; D012331:RNA, Fungal; D029701:Saccharomyces cerevisiae Proteins; C548306:EXO5 protein, S cerevisiae; D005092:Exonucleases