IscR‐dependent gene expression links iron‐sulphur cluster assembly to the control of O <sub>2</sub> ‐regulated genes in <i>Escherichia coli</i>
Bibliographic record
Abstract
IscR is an iron-sulphur (Fe-S) cluster-containing transcription factor that represses transcription of the operon containing its own gene and the iscSUA-hscBA-fdx genes, whose products are involved in Fe-S cluster biogenesis. In this study, global transcriptional profiling of Escherichia coli IscR(+) and IscR(-) strains grown under aerobic and anaerobic conditions indicated that 40 genes in 20 predicted operons were regulated by IscR. DNase I footprinting and/or in vitro transcription reactions identified seven new promoters under direct IscR control. Among these were genes encoding known or proposed functions in Fe-S cluster biogenesis (sufABCDSE, yadR and yhgI) and Fe-S cluster-containing anaerobic respiratory enzymes (hyaABCDEF, hybOABCDEFG and napFDAGHBC). The finding that IscR repressed expression of the hyaA, hybO and napF promoters specifically under aerobic growth conditions suggests a new mechanism to explain their upregulation under anaerobic growth conditions. Phylogenetic footprinting of the DNase I protected regions of seven promoters implies that there are at least two different classes of IscR binding sites conserved among many bacteria. The findings presented here indicate a more general role of IscR in the regulation of Fe-S cluster biogenesis and that IscR contributes to the O(2) regulation of several promoters controlling the expression of anaerobic Fe-S proteins.
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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".