Original Paper

Cell Death and Differentiation (2008) 15, 1838–1846; doi:10.1038/cdd.2008.117; published online 29 August 2008

Fis1 deficiency selects for compensatory mutations responsible for cell death and growth control defects

Edited by R Youle

W-C Cheng1, X Teng2, H K Park1, C M Tucker3, M J Dunham3,4 and J M Hardwick1,2

  1. 1W Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, MD 21205, USA
  2. 2Department of Pharmacology and Molecular Sciences, Johns Hopkins School of Medicine, Baltimore, MD 21205, USA
  3. 3Carl Icahn Laboratory, Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA

Correspondence: JM Hardwick, Department of Molecular Microbiology, Pharmacology, Neurology, Johns Hopkins Bloomberg SPH, 615 N. Wolfe St., MMI E5140, Baltimore, MD 21205, USA. Tel: +410 955 2716; Fax: +410 955 0105; E-mail: hardwick@jhu.edu

4Current address: Department of Genome Sciences, University of Washington, Seattle, WA, USA

Received 14 March 2008; Revised 18 June 2008; Accepted 19 June 2008; Published online 29 August 2008.

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Abstract

Genetic mutations affecting mitochondrial fission and fusion proteins cause human neurological disorders, but are assumed to be well tolerated in yeast. The conserved mitochondrial fission protein Dnm1/Drp1 is required for normal mitochondrial division, but also promotes cell death in mammals and yeast. Fis1, an outer mitochondrial membrane-anchored receptor for Dnm1/Drp1, also can promote cell death in mammals, but appears to have prosurvival activity in yeast. Here we report that deletion of the FIS1 gene in yeast consistently results in acquisition of a secondary mutation that confers sensitivity to cell death. In several independently derived FIS1 knockouts, tiling arrays and genomic sequencing identified the secondary mutation as a premature termination in the same stress-response gene, WHI2. The WHI2 mutation rescues the mitochondrial respiratory defect (petite formation) caused by FIS1 deficiency, but also causes a failure to suppress cell growth during amino-acid deprivation. Thus, loss of Fis1 drives the selection for specific compensatory mutations that confer defective growth control and cell death regulation, characteristic of human tumor cells. The important long-term survival function of Fis1 that is compensated by WHI2 mutation appears to be independent of fission factor Dnm1/Drp1 and its adaptor Mdv1, but may be mediated through a second adaptor Caf4, as WHI2 is also mutated in a CAF4 knockout.

Keywords:

Fis1, WHI2, programmed cell death, mitochondrial fission, apoptosis, Drp1

Abbreviations:

CAF4, CCR4 associated factor; CSH, Cold Spring Harbor Laboratory Press; G418R, G418 resistant; ME, Methods in Enzymology; SCD, synthetic complete dextrose medium; WHI2, whiskey 2; YKO, yeast knockout

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