Pituitary Tumor AP-2α Recognizes a Cryptic Promoter in Intron 4 of Fibroblast Growth Factor Receptor 4
Bibliographic record
Abstract
Fibroblast growth factor receptors (FGFRs) have been implicated in a multitude of proliferative functions, and FGFR4 is expressed differentially in normal and neoplastic pituitary. Human pituitary tumors express a truncated FGFR4 isoform (ptd-FGFR4) for which transcription is initiated from a downstream alternative site. Analysis of FGFR4 intronic sequences predicted a possible promoter within intron 4 (In4) including a classic TATA box with a possible transcriptional start site in intron 5. We show here that the human In4 sequence can direct luciferase reporter activity in transfected pituitary GH4 cells. Four overlapping fragments (A1, A2, B1, and B2) of this intron were examined by electromobility shift assay using nuclear extracts from rat pituitary tumors. Of these, fragment B2 formed complexes with nuclear rat pituitary GH4 extracts that were competed specifically by wild type but not mutant oligonucleotides for the neural crest cell lineage-derived activating transcription factor AP-2. Conversely, an AP-2 consensus sequence probe was competed by the In4 B2 oligonucleotide but not by other fragments of the same intron. The In4 B2 complex was competed partially by NFkappaB, supershifted by an AP-2alpha-specific antibody, and co-migrated with the same probe incubated with recombinant AP-2alpha protein. We also examined the ability of primary human pituitary tumor extracts to interact with the In4 B2 fragment. Pituitary tumor-In4 B2 complexes were competed specifically by wild type AP-2 but not mutant AP-2 oligonucleotides. Western blotting revealed higher levels of AP-2alpha expression in primary human pituitary tumors than in nontumorous tissue. Mutagenesis of the putative AP-2 binding site in In4 B2 resulted in a marked loss of promoter activity in a luciferase assay. AP-2alpha transfection in the presence of the histone deacetylase inhibitor trichostatin-A resulted in enhanced expression of endogenous ptd-FGFR4. These data indicate that a cryptic promoter within intron 4 binds AP-2alpha. AP-2alpha and chromatin changes may contribute to the utilization of an alternative transcription start site leading to the genesis of the tumorigenic ptd-FGFR4 isoform.
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.004 | 0.002 |
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".