TORC2 Signaling Pathway Guarantees Genome Stability in the Face of DNA Strand Breaks

Abstract

A chemicogenetic screen was performed in budding yeast mutants that have a weakened replication stress response. This identified an inhibitor of target of rapamycin (TOR) complexes 1 and 2 that selectively enhances the sensitivity of sgs1Δ cells to hydroxyurea and camptothecin. More importantly, the inhibitor has strong synthetic lethality in combination with either the break-inducing antibiotic Zeocin or ionizing radiation, independent of the strain background. Lethality correlates with a rapid fragmentation of chromosomes that occurs only when TORC2, but not TORC1, is repressed. Genetic inhibition of Tor2 kinase, or its downstream effector kinases Ypk1/Ypk2, conferred similar synergistic effects in the presence of Zeocin. Given that Ypk1/Ypk2 controls the actin cytoskeleton, we tested the effects of actin modulators latrunculin A and jasplakinolide. These phenocopy TORC2 inhibition on Zeocin, although modulation of calcineurin-sensitive transcription does not. These results implicate TORC2-mediated actin filament regulation in the survival of low levels of DNA damage.

Decatransin, a novel natural product inhibiting protein translocation at the Sec61/SecY translocon

“…This might be due to our strategy of inducing mutations rather than selecting spontaneously resistant clones. Multiple mutagenesis experiments in fungi and mammalian cells have revealed that there is a bias towards chromosomal aberrations and SNPs in pleiotropic drug-resistance genes if spontaneous mutants are selected and sequenced (Nyfeler et al, 2012;Richie et al, 2013;Sadlish et al, 2013;Shimada et al, 2013). The underlying mechanism might be that amino acid mutations in the essential, primary target can often be deleterious, and these cells are rapidly outcompeted.…”

Target of Rapamycin Complex 2 Regulates Actin Polarization and Endocytosis via Multiple Pathways

“…50 and data not shown). Recently, we identified BHS345 as a specific inhibitor of TORC1 and TORC2 both in vitro and in yeast (51). BHS345 is structurally similar to BEZ235 (Fig.…”

Glucose Activates TORC2-Gad8 Protein via Positive Regulation of the cAMP/cAMP-dependent Protein Kinase A (PKA) Pathway and Negative Regulation of the Pmk1 Protein-Mitogen-activated Protein Kinase Pathway

“…Recently, we have showed that TORC2 is required under DNA replication stress and for maintenance of telomere length and gene silencing (12). Interestingly, a role for TORC2 in maintenance of genome stability has also been reported in Saccharomyces cerevisiae (13), suggesting that the role of TORC2 in tolerance to DNA damage and genome integrity is conserved in evolution.…”