Transcriptional co-operativity between distant retinoic acid response elements in regulation of<i>Cyp26A1</i>inducibility
Bibliographic record
Abstract
Cyp26A1 encodes an RA (retinoic acid)-catabolizing CYP (cytochrome P450) protein that plays a critical role in regulating RA distribution in vivo. Cyp26A1 expression is inducible by RA, and the locus has previously been shown to contain a RARE (RA response element), R1, within the minimal promoter [Loudig, Babichuk, White, Abu-Abed, Mueller and Petkovich (2000) Mol. Endocrinol. 14, 1483-1497]. In the present study, we report the identification of a second functional RARE (R2) located 2.0 kb upstream of the Cyp26A1 transcriptional start site. Constructs containing murine sequences encompassing both R1 and R2 showed that these elements work together to generate higher transcriptional activity upon treatment with RA than those containing R1 alone. Inclusion of R2 also dramatically enhanced the sensitivity of reporter constructs to RA, as even treatment with 10(-8) M RA resulted in a 5-fold induction of reporter activity. Mutational analysis identified R2 as the functional element responsible for the increased RA inducibility of promoter constructs. The element was shown to bind RARgamma (RA receptor gamma)/RXRalpha (retinoid X receptor alpha) heterodimers in vitro, and inclusion of nuclear receptors in transfections boosted the transcriptional response. A construct containing both R1 and R2 was used to generate a stable luciferase reporter cell line that can be used as a tool to identify factors regulating Cyp26A1 expression. The analysis of R1 and R2 has led to the proposal that the two elements work synergistically to provide a maximal response to RA and that R2 is an upstream enhancer.
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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 | 0.001 |
| 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 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
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".