Components of Golgi‐to‐vacuole trafficking are required for nitrogen‐ and TORC1‐responsive regulation of the yeast GATA factors

Abstract

Nitrogen catabolite repression (NCR) is the regulatory pathway through which Saccharomyces cerevisiae responds to the available nitrogen status and selectively utilizes rich nitrogen sources in preference to poor ones. Expression of NCR-sensitive genes is mediated by two transcription activators, Gln3 and Gat1, in response to provision of a poorly used nitrogen source or following treatment with the TORC1 inhibitor, rapamycin. During nitrogen excess, the transcription activators are sequestered in the cytoplasm in a Ure2-dependent fashion. Here, we show that Vps components are required for Gln3 localization and function in response to rapamycin treatment when cells are grown in defined yeast nitrogen base but not in complex yeast peptone dextrose medium. On the other hand, Gat1 function was altered in vps mutants in all conditions tested. A significant fraction of Gat1, like Gln3, is associated with light intracellular membranes. Further, our results are consistent with the possibility that Ure2 might function downstream of the Vps components during the control of GATA factor-mediated gene expression. These observations demonstrate distinct media-dependent requirements of vesicular trafficking components for wild-type responses of GATA factor localization and function. As a result, the current model describing participation of Vps system components in events associated with translocation of Gln3 into the nucleus following rapamycin treatment or growth in nitrogen-poor medium requires modification.

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

“…The remaining 6 genes identified in the screen encode proteins functioning in protein folding, mitochondrial ribosome assembly, the glutathione cycle, and arginine biosynthesis, as well as the TORC1-interacting protein Toc1p, and the GATA transcription factor Gaf1. In budding yeast, components of Golgi-to-vacuole trafficking are required for nitrogen-and TORC1-responsive regulation of GATA factors (Fayyadkazan et al, 2014;Puria et al, 2008). The screen results suggest that functional relationships between GATA factors and intracellular vesicles are conserved in fission yeast.…”

Yeast nitrogen catabolite repression is sustained by signals distinct from glutamine and glutamate reservoirs

“…, panel B), we analyzed the transcription of another NCR‐sensitive gene, DAL5 (Fig. , panel A), because its expression is known to require the simultaneous activity of both Gln3 and Gat1 under derepressive conditions (Georis et al ., ; Fayyadkazan et al ., ). As anticipated, DAL5 transcription remained low in Am + Gln‐grown gdh1Δ cells (Fig.…”

“…, panels A and C). It is noteworthy that inhibition of DAL5 expression in pro‐grown cells is known to require inactivation of either Gln3 or Gat1 (Fayyadkazan et al ., ), whereas the impairment of GAP1 expression requires the simultaneous inactivation of both GATA activators (Georis et al ., ). Hence, our data suggest that the transient glutamine increase, after 10 min of ammonium addition, would inhibit the activity of both GATA factors, whereas after 16 h, one of the GATA factors would partially activate GAP1 expression.…”

“…TORC1 activity is controlled by different upstream regulators highly conserved between yeast and mammalian cells (Dubouloz et al ., ; Kim et al ., ; Binda et al ., ; Sancak et al ., ; Bonfils et al ., ; Han et al ., ; Panchaud et al ., ). However, a role for most of those regulators in NCR has not been described so far, and a growing literature suggests that TORC1 is not the only regulator controlling GATA factor activity (Cox et al ., ; Tate et al ., 2005; 2006; 2010; Puria et al ., ; Georis et al ., ; Feller et al ., ; Rai et al ., ; Tate and Cooper, ; Fayyadkazan et al ., ). One prominent observation is that Gln3 nuclear localization is more responsive to poor nitrogen supply than rapamycin treatment, indicating that TORC1 inactivation does not totally mimic non‐preferred nitrogen supplementation with respect to GATA factor localization (Tate et al ., ; Georis et al ., ).…”

Nitrogen Starvation and TorC1 Inhibition Differentially Affect Nuclear Localization of the Gln3 and Gat1 Transcription Factors Through the Rare Glutamine tRNACUG in Saccharomyces cerevisiae

“…This is roughly the same amount of time required for nuclear Gln3 entry to be lost when a sup70-65 single mutant is shifted to 30°. Importantly, cells with deletions of URE2 also exhibit synthetic loss of growth with mutations in VPS Class C and D proteins (vps3,vps34,vps45,pep3) that participate in endomembrane vesicular trafficking (Fayyadkazan et al 2014). These synthetic interactions, along with the observations that (1) Gln3-Myc 13 associates with a tubular membranous structures as it enters and exits the nucleus (Cox et al 2002(Cox et al , 2004 and (2) Gln3-Myc 13 partially co-localizes with Vps10, a late-Golgi/endosomal marker (Puria et al 2008;Nickerson et al 2009;Kingsbury et al 2014), suggest that the component or complex that is specifically sensitive to glutamine tRNA CUG alteration and required for nuclear Gln3 entry may well be associated with the membranous system Gln3 uses when entering and exiting the nucleus.…”