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Role of the putative structural protein Sed1p in mitochondrial genome maintenance

Naina Phadnis1, Elaine Ayres Sia

  • 1Department of Biology, University of Rochester, Rochester, NY 14627-0211, USA.

Journal of Molecular Biology
|September 8, 2004
PubMed

Insights

The yeast protein Sed1p is crucial for maintaining mitochondrial genome stability. Deleting SED1 increases mitochondrial DNA mutations and respiration loss, indicating Sed1p

Area of Science:

  • Mitochondrial biology
  • Molecular genetics
  • Cell biology

Background:

  • The mitochondrial genome requires numerous proteins for replication and segregation.
  • The nuclear gene MIP1 encodes the mitochondrial DNA polymerase in Saccharomyces cerevisiae.
  • Other factors involved in mitochondrial genome maintenance remain largely uncharacterized.

Purpose of the Study:

  • To identify novel factors involved in mitochondrial genome maintenance.
  • To investigate the function of the yeast protein Sed1p in relation to mitochondrial DNA replication.

Main Methods:

  • Bacterial two-hybrid screening using Mip1p as bait.
  • In vitro interaction assays.
  • Analysis of mitochondrial DNA mutation rates and respiration loss in sed1 deletion mutants.
  • Indirect immunofluorescence microscopy for protein localization.
  • Biochemical fractionation of mitochondrial components.

Main Results:

  • Sed1p was identified as a Mip1p-interacting protein.
  • Sed1p is a cell surface protein with modified forms, the largest of which interacts with Mip1p.
  • Deletion of SED1 significantly increased mitochondrial DNA point mutation rates and respiration loss.
  • Sed1p localizes to mitochondria and is found in purified mitochondrial fractions.
  • Sed1p deletion reduced Mip1p levels and affected Cox3p expression.

Conclusions:

  • Sed1p plays a critical role in maintaining mitochondrial genome stability.
  • Sed1p is a novel factor involved in mitochondrial DNA maintenance.
  • Sed1p's function is specific to the mitochondrial genome, not the nuclear genome.

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