Differential Regulation of Transcription Factors Stp1 and Stp2 in the Ssy1-Ptr3-Ssy5 Amino Acid Sensing Pathway

Abstract

Stp1 and Stp2 are two homologous transcription factors activated in response to extracellular amino acid stimuli. Here we show that both ubiquitin-dependent degradation of Stp1 and Stp2 and their intracellular localization are differentially regulated. We have found that the E2 ubiquitinconjugating enzyme Cdc34 is required for degradation of both full-length and processed Stp1, but not Stp2. We have also found that Grr1, the F-box component of the SCF Grr1 E3 ubiquitin ligase, is the primary factor in degradation of full-length Stp1, whereas both Grr1 and Cdc4 are required for degradation of processed Stp1. Our localization studies showed that full-length Stp1 is localized both in the cytoplasm and at the cell periphery, whereas full-length Stp2 is localized only diffusely in the cytoplasm. We identified two nuclear localization signals of Stp1 and found that the Nterminal domain of Stp1 is required for localization of fulllength Stp1 to the cell periphery. We also found that Stp2 is the primary factor involved in basal activation of target gene expression. Our results indicate that the functions of two seemingly redundant transcription factors can be separated by differential degradation and distinct cellular localization.

Reduced Ssy1-Ptr3-Ssy5 (SPS) Signaling Extends Replicative Life Span by Enhancing NAD+ Homeostasis in Saccharomyces cerevisiae

“…STP1 and STP2 are homologous SPS downstream transcription factors that share overlapping function (30,34). These results support that the RLS extension observed in the ssy5⌬ mutant was due to overall reduction in SPS activity.…”

Regulation of Amino Acid, Nucleotide, and Phosphate Metabolism in Saccharomyces cerevisiae

“…Upon induction by extracellular amino acids, the SPS sensor catalyzes an endoproteolytic processing event that cleaves the regulatory N-terminal domains. The shorter forms of Stp1 and Stp2 efficiently target to the nucleus where they bind promoters of a limited set of genes, including a subset of broad-specificity amino acid permeases (cluster 1, Table 4) and the peptide transporter Ptr2 (Didion et al 1996(Didion et al , 1998de Boer et al 1998de Boer et al , 2000Iraqui et al 1999;Klasson et al 1999;Wielemans et al 2010;Tumusiime et al 2011).…”

Glutamate dehydrogenase (Gdh2)-dependent alkalization is dispensable for escape from macrophages and virulence ofCandida albicans

“…For C-terminal GFP tagging of Gdh2, an approximately 2.8 kB of PCR cassette was amplified from plasmid pFA-GFPγ- URA3 (38) using primers (p7/p8). The amplicon was purified and then introduced into CAI4 ( ura3 / ura3 ).…”