title: Gad8 Protein Is Found in the Nucleus Where It Interacts with the MluI Cell Cycle Box-binding Factor (MBF) Transcriptional Complex to Regulate the Response to DNA Replication Stress.
abstract: The target of rapamycin (TOR) kinase is found at the core of two evolutionarily conserved complexes known as TOR complexes 1 and 2 (TORC1 and TORC2). In fission yeast, TORC2 is dispensable for proliferation under optimal growth conditions but is required for starvation and stress responses. We have previously reported that loss of function of TORC2 renders cells highly sensitive to DNA replication stress; however, the mechanism underlying this sensitivity is unknown. TORC2 has one known direct substrate, the kinase Gad8, which is related to AKT in human cells. Here we show that both TORC2 and its substrate Gad8 are found in the nucleus and are bound to the chromatin. We also demonstrate that Gad8 physically interacts with the MluI cell cycle box-binding factor (MBF) transcription complex that regulates the G1/S progression and the response to DNA stress. In mutant cells lacking TORC2 or Gad8, the binding of the MBF complex to its cognate promoters is compromised, and the induction of MBF target genes in response to DNA replication stress is reduced. Consistently, the protein levels of Cdt2 and Cig2, two MBF target genes, are reduced in the absence of TORC2-Gad8 signaling. Taken together, our findings highlight critical functions of TORC2 in the nucleus and suggest a role in surviving DNA replication stress via transcriptional regulation of MBF target genes.
authors.affiliation: From the Department of Natural and Life Sciences, The Open University of Israel, University Road 1, 4353701 Raanana, Israel and.
authors.forename: Adiel
authors.initials: A
authors.lastname: Cohen
authors.affiliation: Department of Molecular Microbiology and Biotechnology, Tel Aviv University, 69978 Tel Aviv, Israel.
authors.forename: Martin
authors.initials: M
authors.lastname: Kupiec
authors.affiliation: From the Department of Natural and Life Sciences, The Open University of Israel, University Road 1, 4353701 Raanana, Israel and ronitwe@openu.ac.il.
authors.forename: Ronit
authors.initials: R
authors.lastname: Weisman
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D019926:Cyclin B / Q000235:genetics / Q000378:metabolism; D004249:DNA Damage; D016193:G1 Phase / Q000235:genetics; D000076225:Mechanistic Target of Rapamycin Complex 2; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D016196:S Phase / Q000235:genetics; D012568:Schizosaccharomyces / Q000235:genetics / Q000378:metabolism*; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000235:genetics; D058570:TOR Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C506543:Cdt2 protein, S pombe; D018797:Cell Cycle Proteins; C080328:Cig2 protein, S pombe; D019926:Cyclin B; C489911:DSC1 protein, S pombe; D046912:Multiprotein Complexes; D029702:Schizosaccharomyces pombe Proteins; D014157:Transcription Factors; C476401:Gad8 protein, S pombe; D000076225:Mechanistic Target of Rapamycin Complex 2; D017346:Protein Serine-Threonine Kinases; D058570:TOR Serine-Threonine Kinases
keywords: DNA binding protein; DNA damage response; Gad8; MBF; S. pombe; cell cycle; target of rapamycin (TOR); yeast