A dynamic transcriptional network communicates growth potential to ribosome synthesis and critical cell size.

By Paul Jorgensen, I. Rupes̆, J. Sharom, Lisa M. Schneper, James R. Broach, Mike Tyers. Genes & Development, 2004

667 citations recorded by the source corpus.

Cell-size homeostasis entails a fundamental balance between growth and division. The budding yeast Saccharomyces cerevisiae establishes this balance by enforcing growth to a critical cell size prior to cell cycle commitment (Start) in late G1 phase. Nutrients modulate the critical size threshold, such that cells are large in rich medium and small in poor medium. Here, we show that two potent negative regulators of Start, Sfp1 and Sch9, are activators of the ribosomal protein (RP) and ribosome biogenesis (Ribi) regulons, the transcriptional programs that dictate ribosome synthesis rate in accord with environmental and intracellular conditions. Sfp1 and Sch9 are required for carbon-source modulation of cell size and are regulated at the level of nuclear localization and abundance, respectively. Sfp1 nuclear concentration responds rapidly to nutrient and stress conditions and is regulated by the Ras/PKA and TOR signaling pathways. In turn, Sfp1 influences the nuclear localization of Fhl1 and Ifh1, which bind to RP gene promoters. Starvation or the absence of Sfp1 causes Fhl1 and Ifh1 to localize to nucleolar regions, concomitant with reduced RP gene transcription. These findings suggest that nutrient signals set the critical cell-size threshold via Sfp1 and Sch9-mediated control of ribosome biosynthetic rates.

Subfields: Molecular Biology

View Paper: https://www.semanticscholar.org/paper/e22c9dc30af8ab6ba5be2212b73ddcce2412bddd

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Cytoplasmic 5′-3′ exonuclease Xrn1p is also a genome-wide transcription factor in yeast (2013, background): “All these GO categories are closely linked to the genes belonging to the RiBi (Ribosome Biogenesis) regulon (Jorgensen et al., 2004) or to ribosomal protein (RP) genes.”
Nutrient sensing and signaling in the yeast Saccharomyces cerevisiae (2014, background): “One of the main TORC1-regulated roles of Sch9 is to modulate translation and cell size attained before cell division (Jorgensen et al., 2002, 2004).”
Extension of chronological life span in yeast by decreased TOR pathway signaling. (2006, background): “…in the presence of ample nutrients, especially glucose, and Sch9 and PKA are thought to signal in parallel pathways to increase glycolysis, ribosome biogenesis , growth, and cell cycle progression and to inhibit stress response pathways (Longo 2003; Jorgensen et al. 2004; Roosen et al. 2005).”
TOR signaling in growth and metabolism. (2006, background): “TOR controls RP genes also via the Zn finger transcription factor SFP1 that binds and regulates RP gene promoters in a TOR-dependent manner (Jorgensen et al., 2004).”
How cells coordinate growth and division. (2004, background): “A final problem with the Cln3 abudance model is that the size of WHI1-1 and cln3∆ cells responds appropriately to nutrient modulation [68,95].”
Ribosomal proteins: functions beyond the ribosome. (2015, background): “Consistently, several transcription factors, such as SFP1 (Jorgensen et al., 2004; Marion et al., 2004) and FHL1 (Martin et al., 2004; Schawalder et al., 2004; Rudra et al., 2005), were found to directly associate with RP gene promoters, activating their transcription under growth-favorable…”
Target of Rapamycin (TOR) in Nutrient Signaling and Growth Control (2011, background): “Although physical interaction with RiBi promoters has not been reported, overexpression of Sfp1 causes a rapid upregulation of most RiBi genes, suggesting that Sfp1 also regulates this important regulon (Jorgensen et al. 2004).”
Yeasts in food and beverages (2006, background): “Under optimal growth conditions, Sfp1 is localised to the nucleus and regulates ribosomal protein gene expression but upon inhibiting TOR signalling, stress or changes in nutrient availability, Sfp1 is released from the ribosomal protein gene promoters and translocates to the cytoplasm (Jorgensen et”
Nutritional Control of Growth and Development in Yeast (2012, background): “The nature of quiescence and the role of signaling pathways in orchestrating quiescence have been described in several excellent reviews (Gray et al. 2004; Smets et al. 2010; De Virgilio 2011).”