A dynamic transcriptional network communicates growth potential to ribosome synthesis and critical cell size
Bibliographic record
Abstract
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.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".