AraC/XylS family members, HilD and HilC, directly activate virulence gene expression independently of HilA in <i>Salmonella typhimurium</i>
Bibliographic record
Abstract
Salmonella typhimurium is a Gram-negative enteric pathogen that can infect intestinal epithelial cells and induce inflammation of the intestinal mucosa. These processes are mediated by a type III secretion system (TTSS), which is encoded on Salmonella pathogenicity island 1 (SPI1). Previous studies showed that four SPI1-encoded transcriptional regulators, HilD, HilC, HilA and InvF, act in an ordered fashion to co-ordinately activate expression of the SPI1 TTSS. HilD and HilC derepress hilA transcription. HilA activates invF as well as SPI1 genes that encode components of the TTS apparatus. InvF then activates genes that encode proteins secreted by the SPI1 TTS apparatus. In this scheme, HilD and HilC indirectly activate expression of the SPI1 TTS apparatus and its secreted substrates by affecting hilA expression. Here, we report that HilD and HilC can also activate expression of a subset of SPI1 genes independently of HilA. Our studies show that HilD and HilC activate transcription of invF from a promoter that is far upstream of its HilA-dependent promoter. This activation is most probably through direct binding of HilD and HilC to sequences upstream and downstream of this alternative HilA-independent promoter. We conclude that HilD and HilC have a second role in SPI1 gene regulation that is separate from their role in co-ordinating expression of the SPI1 TTSS through hilA.
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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 | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 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) | 0.000 | 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".