title: Evolutionarily conserved genetic interactions with budding and fission yeast MutS identify orthologous relationships in mismatch repair-deficient cancer cells.
abstract: BACKGROUND
  The evolutionarily conserved DNA mismatch repair (MMR) system corrects base-substitution and insertion-deletion mutations generated during erroneous replication. The mutation or inactivation of many MMR factors strongly predisposes to cancer, where the resulting tumors often display resistance to standard chemotherapeutics. A new direction to develop targeted therapies is the harnessing of synthetic genetic interactions, where the simultaneous loss of two otherwise non-essential factors leads to reduced cell fitness or death. High-throughput screening in human cells to directly identify such interactors for disease-relevant genes is now widespread, but often requires extensive case-by-case optimization. Here we asked if conserved genetic interactors (CGIs) with MMR genes from two evolutionary distant yeast species (Saccharomyces cerevisiae and Schizosaccharomyzes pombe) can predict orthologous genetic relationships in higher eukaryotes.
  
  
  METHODS
  High-throughput screening was used to identify genetic interaction profiles for the MutSα and MutSβ heterodimer subunits (msh2Δ, msh3Δ, msh6Δ) of fission yeast. Selected negative interactors with MutSβ (msh2Δ/msh3Δ) were directly analyzed in budding yeast, and the CGI with SUMO-protease Ulp2 further examined after RNA interference/drug treatment in MSH2-deficient and -proficient human cells.
  
  
  RESULTS
  This study identified distinct genetic profiles for MutSα and MutSβ, and supports a role for the latter in recombinatorial DNA repair. Approximately 28% of orthologous genetic interactions with msh2Δ/msh3Δ are conserved in both yeasts, a degree consistent with global trends across these species. Further, the CGI between budding/fission yeast msh2 and SUMO-protease Ulp2 is maintained in human cells (MSH2/SENP6), and enhanced by Olaparib, a PARP inhibitor that induces the accumulation of single-strand DNA breaks. This identifies SENP6 as a promising new target for the treatment of MMR-deficient cancers.
  
  
  CONCLUSIONS
  Our findings demonstrate the utility of employing evolutionary distance in tractable lower eukaryotes to predict orthologous genetic relationships in higher eukaryotes. Moreover, we provide novel insights into the genome maintenance functions of a critical DNA repair complex and propose a promising targeted treatment for MMR deficient tumors.
authors.affiliation: Department of Cell Biology, Albert Einstein College of Medicine, New York, USA.
authors.forename: Elena
authors.initials: E
authors.lastname: Tosti
authors.affiliation: Department of Microbiology & Immunology, Albert Einstein College of Medicine, New York, USA.
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Katakowski
authors.affiliation: Department of Cell Biology, Albert Einstein College of Medicine, New York, USA.
authors.forename: Sonja
authors.initials: S
authors.lastname: Schaetzlein
authors.affiliation: Department of Cell Biology, Albert Einstein College of Medicine, New York, USA.
authors.forename: Hyun-Soo
authors.initials: HS
authors.lastname: Kim
authors.affiliation: Department of Cellular & Molecular Pharmacology, UCSF, San Francisco, USA ; California Institute for Quantitative Biosciences, San Francisco, USA ; School of Medicine and Medical Science, University College Dublin, Dublin, Ireland.
authors.forename: Colm J
authors.initials: CJ
authors.lastname: Ryan
authors.affiliation: Department of Cellular & Molecular Pharmacology, UCSF, San Francisco, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Shales
authors.affiliation: Department of Cellular & Molecular Pharmacology, UCSF, San Francisco, USA.
authors.forename: Assen
authors.initials: A
authors.lastname: Roguev
authors.affiliation: Department of Cellular & Molecular Pharmacology, UCSF, San Francisco, USA ; California Institute for Quantitative Biosciences, San Francisco, USA ; J. David Gladstone Institutes, San Francisco, USA.
authors.forename: Nevan J
authors.initials: NJ
authors.lastname: Krogan
authors.affiliation: Department of Microbiology & Immunology, Albert Einstein College of Medicine, New York, USA.
authors.forename: Deborah
authors.initials: D
authors.lastname: Palliser
authors.affiliation: Department of Cell Biology, Albert Einstein College of Medicine, New York, USA.
authors.forename: Michael-Christopher
authors.initials: MC
authors.lastname: Keogh
authors.affiliation: Department of Cell Biology, Albert Einstein College of Medicine, New York, USA.
authors.forename: Winfried
authors.initials: W
authors.lastname: Edelmann