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Growth-based Determination and Biochemical Confirmation of Genetic Requirements for Protein Degradation in Saccharomyces cerevisiae
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A role for ubiquitination in mitochondrial inheritance in Saccharomyces cerevisiae

H A Fisk1, M P Yaffe

  • 1University of California, San Diego, Department of Biology, La Jolla, California 92093, USA.

The Journal of Cell Biology
|June 15, 1999
PubMed

Insights

The smm1 mutation in yeast reveals that the Rsp5p ubiquitin ligase is crucial for mitochondrial inheritance. Protein ubiquitination is essential for maintaining proper mitochondrial function and distribution.

Area of Science:

  • Cell Biology
  • Genetics
  • Biochemistry

Background:

  • Mitochondrial distribution and morphology are critical for cellular function.
  • The mdm1-252 mutation in Saccharomyces cerevisiae causes defects in mitochondrial inheritance.
  • Understanding the genetic and molecular mechanisms regulating mitochondrial inheritance is essential.

Purpose of the Study:

  • To investigate the role of the smm1 mutation in suppressing mitochondrial defects.
  • To identify the gene responsible for the smm1 mutation and elucidate its function.
  • To determine the involvement of protein ubiquitination in mitochondrial inheritance.

Main Methods:

  • Genetic screening for suppressors of mdm1-252 defects.
  • Gene mapping and identification of the smm1 locus.
  • Analysis of yeast growth, mitochondrial morphology, and inheritance.
  • Ubiquitin-protein ligase activity assays.
  • Site-directed mutagenesis and gene overexpression studies.

Main Results:

  • The smm1 mutation suppresses mdm1-252-induced mitochondrial defects.
  • smm1 maps to RSP5, encoding the essential ubiquitin-protein ligase Rsp5p.
  • Rsp5p's ligase activity is essential for mitochondrial inheritance.
  • Overexpression of wild-type ubiquitin suppresses smm1 defects, while a K63R mutant ubiquitin exacerbates them.
  • A second suppressor, smm2, maps to BUL1, a Rsp5p-interacting protein.

Conclusions:

  • Protein ubiquitination mediated by Rsp5p is essential for mitochondrial inheritance in yeast.
  • Rsp5p plays a critical role in regulating mitochondrial distribution and morphology.
  • This study reveals a novel function for protein ubiquitination in cellular processes.

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