The GATA transcription factor Gaf1 represses tRNA genes, inhibits growth, and extends chronological lifespan downstream of fission yeast TORC1

Abstract

Target of Rapamycin Complex 1 (TORC1) signaling promotes growth and ageing. Inhibition of TORC1 leads to a down-regulation of factors that stimulate protein translation, including RNA polymerase III, which in turn contributes to longevity. TORC1-mediated posttranscriptional regulation of protein translation has been well studied, while analogous transcriptional regulation is less well understood. Here we screened fission yeast deletion mutants for resistance to Torin1, which inhibits TORC1 and cell growth. Mutants lacking the GATA transcription factor Gaf1 (gaf1Δ) grew normally even in high doses of Torin1. The gaf1Δ mutants shortened the chronological lifespan of non-dividing cells and diminished the lifespan extension triggered by Torin1 treatment. Expression profiling and genome-wide binding experiments showed that, after TORC1 inhibition, Gaf1 directly up-regulated genes for small-molecule metabolic pathways and indirectly repressed genes for protein translation.Surprisingly, Gaf1 also bound to the tRNA genes and down-regulated them, so functions as a transcription factor for genes transcribed by RNA polymerase III. We conclude that Gaf1 controls the transcription of both coding and tRNA genes to inhibit translation and growth downstream of TORC1.

Caffeine Stabilises Fission Yeast Wee1 in a Rad24-Dependent Manner but Attenuates Its Expression in Response to DNA Damage

“…In contrast to its effects on HU sensitivity, torin1 was far more effective at sensitising wt cells to phleomycin than caffeine ( Figure 5 C,D). Similar results were obtained with gaf1 Δ mutants, a transcription factor that partially mediates the effect of torin1 on aging [ 29 , 30 ], ( Figure 5 E and Figure 6 B). In addition, gaf1 Δ mutants exposed to phleomycin and torin1 were shorter than cells exposed to phleomycin alone ( Figure 6 C).…”

Caffeine stabilises fission yeast Wee1 in a Rad24-dependent manner but attenuates its expression in response to DNA damage identifying a putative role for TORC1 in mediating its effects on cell cycle progression

“…In contrast to its effects on HU sensitivity, torin1 was far more effective at sensitising wt cells to phleomycin than caffeine . Similar results were obtained with gaf1Δ mutants, a transcription factor that partially mediates the effect of torin1 (Laor et al, 2015, Rodríguez-López et al, 2019. In addition, gaf1Δ mutants exposed to phleomycin and torin1 were shorter than cell exposed to phleomycin alone ( Fig.…”

“…Mik1 expression and global 26S proteasome-mediated protein degradation (Alao et al, unpublished results). The TORC1 downstream transcription factor Gaf1 has recently been shown to mediate the effects of Tor2 inhibition on chronological lifespan in S. pombe (Laor et al, 2015, Rodríguez-López et al, 2019. Caffeine and torin1 clearly increased sensitivity to phleomycin in gaf1Δ mutants, suggesting this effect occurs independently of Gaf1.…”

Mitochondrial respiration is required to provide amino acids during fermentative proliferation of fission yeast

“…4C; Fig. S5C) [45]. Accordingly, this group was enriched for genes that are repressed or induced, respectively, upon genetic activation or inhibition of TOR kinase signalling ( Fig.…”

“…The same analysis was performed for mutants grown on EMM (left) or on EMM supplemented with antimycin A (right) ( Table S2). ) after one hour of inhibiting TOR kinase with torin1 or caffeine/rapamycin treatment relative to cell before treatment; cells were grown in rich media -YES (data from [45]) (D) Overlaps between genes repressed with arginine supplementation and genes induced in tor2 thermo-sensitive mutant (p <E-27) [48], or repressed in strains deleted for the TOR inhibitors tsc1 and tsc2 (p <E-16) [47]. (E) Enriched and underrepresented amino acids in proteins encoded by 40 genes that are downregulated in media with arginine.…”