title: Tryptophan-Dependent Control of Colony Formation After DNA Damage via Sea3-Regulated TORC1 Signaling in Saccharomyces cerevisiae.
abstract: The Saccharomyces cerevisiae Iml1 complex inhibits TORC1 signaling and SEACAT antagonizes the Iml1 complex. Conditions in which SEACAT functions to inhibit Iml1 and, hence, TORC1 signaling, remain largely unknown. The SEACAT member Sea3 was linked previously to telomere maintenance and DNA repair via genome-wide genetic and physical interaction studies. Therefore, we questioned whether Sea3 functioned through TORC1 to influence these pathways. Deletion of SEA3 delayed the emergence of telomerase-independent survivors that use break-induced replication (BIR) to maintain their telomeres. Similarly, sea3∆ mutants exhibited a delay in colony formation in a BIR assay strain after double-strand break (DSB) induction as well as on the DNA-damaging agent bleomycin. Deletion of IML1 rescued the impaired growth of sea3∆ mutants after DNA damage, consistent with Sea3 functioning as a regulator of TORC1 signaling. The delay was not attributable to slowed DSB repair or termination of the DNA damage checkpoint but to tryptophan auxotrophy. High levels of tryptophan in yeast peptone dextrose media did not rescue the delay in colony formation, suggesting a defect in tryptophan import, although levels of the high-affinity tryptophan permease Tat2 were not perturbed in the sea3Δ mutant. Addition of quinolinic acid, an intermediate of the de novo NAD+ biosynthetic pathway, however, rescued the delay in colony formation in the sea3Δ mutant. Together, these findings highlight the importance of enforcement of TORC1 signaling and suggest that internal tryptophan levels influence growth recovery post DNA damage through the role of tryptophan in NAD+ synthesis.
authors.affiliation: Integrative Molecular and Biomedical Sciences Graduate Program, Baylor College of Medicine, Houston, Texas 77030.
authors.forename: Erica J
authors.identifier: http://orcid.org/0000-0001-6547-3624
authors.initials: EJ
authors.lastname: Polleys
authors.affiliation: Integrative Molecular and Biomedical Sciences Graduate Program, Baylor College of Medicine, Houston, Texas 77030 Department of Pediatrics and Department of Molecular & Human Genetics, Baylor College of Medicine, Houston, Texas 77030 abertuch@bcm.edu.
authors.forename: Alison A
authors.identifier: http://orcid.org/0000-0003-1864-8502
authors.initials: AA
authors.lastname: Bertuch
mesh_terms: D026905:Amino Acid Transport Systems / Q000378:metabolism; D001761:Bleomycin / Q000633:toxicity; D004249:DNA Damage / Q000187:drug effects; D004260:DNA Repair; D005690:Galactose / Q000494:pharmacology; D000076222:Mechanistic Target of Rapamycin Complex 1; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism*; D009243:NAD / Q000096:biosynthesis; D017378:Quinolinic Acid / Q000494:pharmacology; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D058570:TOR Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D016615:Telomere / Q000378:metabolism; D014364:Tryptophan / Q000378:metabolism*
chemical_list: D026905:Amino Acid Transport Systems; C570233:Iml1 protein, S cerevisiae; D008565:Membrane Proteins; D046912:Multiprotein Complexes; C000607393:SEA3 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C429825:TAT2 protein, S cerevisiae; D009243:NAD; D001761:Bleomycin; D014364:Tryptophan; D000076222:Mechanistic Target of Rapamycin Complex 1; D058570:TOR Serine-Threonine Kinases; D017378:Quinolinic Acid; D005690:Galactose
keywords: DNA damage; Iml1 complex; Sea3; TORC1; tryptophan