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The carboxyl‐terminal extension on fungal mitochondrial DNA polymerases: identification of a critical region of the enzyme from Saccharomyces cerevisiae
Author(s) -
Young Matthew J.,
Theriault Steven S.,
Li Mingyi,
Court Deborah A.
Publication year - 2006
Publication title -
yeast
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.923
H-Index - 102
eISSN - 1097-0061
pISSN - 0749-503X
DOI - 10.1002/yea.1344
Subject(s) - biology , saccharomyces cerevisiae , mitochondrial dna , polymerase , genetics , dna polymerase , yeast , biochemistry , microbiology and biotechnology , dna , gene
Abstract Fungal mitochondrial DNA (mtDNA) polymerases, in comparison to their metazoan counterparts, harbour unique carboxyl‐terminal extensions (CTEs) of varying lengths and unknown function. To determine the essential regions of the 279 residue CTE of the yeast enzyme (Mip1p), several CTE‐truncation variants were expressed in Saccharomyces cerevisiae . The respiratory competence of mip1 Δ 175 cells, in which Mip1p lacks the C‐terminal 175 residues, is indistinguishable from that of wild‐type. In contrast, strains harbouring Mip1pΔ351 and Mip1pΔ279 rapidly lose mtDNA. Approximately one in six mip1 Δ 216 transformants grew on glycerol, albeit poorly. Fluorescence microscopy and Southern blot analysis revealed lower levels of mtDNA in these cells, and the rapid loss of mtDNA during fermentative, but not respiratory, growth. Therefore, only the polymerase‐proximal segment of the Mip1p CTE is necessary for mitochondrial function. Comparison of this essential segment with the sequences of other fungal mtDNA polymerases revealed novel features shared among the mtDNA polymerases of the Saccharomycetales. Copyright © 2006 John Wiley & Sons, Ltd.