Double locking of an <i>Escherichia coli</i> promoter by two repressors prevents premature colicin expression and cell lysis
Bibliographic record
Abstract
The synthesis of Eschericha coli colicins is lethal to the producing cell and is repressed during normal growth by the LexA transcription factor, which is the master repressor of the SOS system for repair of DNA damage. Following DNA damage, LexA is inactivated and SOS repair genes are induced immediately, but colicin production is delayed and induced only in terminally damaged cells. The cause of this delay is unknown. Here we identify the global transcription repressor, IscR, as being directly responsible for the delay in colicin K expression during the SOS response, and identify the DNA target for IscR at the colicin K operon promoter. Our results suggest that, IscR stabilizes LexA at the cka promoter after DNA damage thus, preventing its cleavage and inactivation, and this cooperation ensures that suicidal colicin K production is switched on only as a last resort. A similar mechanism operates at the regulatory region of other colicins and, hence, we suggest that many promoters that control the expression of 'lethal' genes are double locked.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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 | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".