Decreased expression of BRCA1 in SK-BR-3 cells is the result of aberrant activation of the GABP Beta promoter by an NRF-1-containing complex
Bibliographic record
Abstract
BACKGROUND: BRCA1 has recently been identified as a potential regulator of mammary stem/progenitor cell differentiation, and this function may explain the high prevalence of breast cancer in BRCA1 mutation carriers, as well as the downregulation of BRCA1 in a large proportion of sporadic breast cancers. That is, loss of BRCA1 function results in blocked differentiation with expansion of the mammary stem/progenitor cells. Because BRCA1 also maintains genomic integrity, its loss could produce a pool of genetically unstable stem/progenitor cells that are prime targets for further transforming events. Thus, elucidating the regulatory mechanisms of BRCA1 expression is important to our understanding of normal and malignant breast differentiation. RESULTS: Loss of BRCA1 expression in the ErbB2-amplified SK-BR-3 cell line was found to be the result of loss of activity of the ets transcription factor GABP, a previously characterized regulator of BRCA1 transcription. The expression of the non-DNA binding GABPβ subunit was shown to be deficient, while the DNA binding subunit, GABPα was rendered unstable by the absence of GABPβ. Deletion analysis of the GABPβ proximal promoter identified a potential NRF-1 binding site as being critical for expression. Supershift analysis, the binding of recombinant protein and chromatin immunoprecipitation confirmed the role of NRF-1 in regulating the expression of GABPβ. The siRNA knockdown of NRF-1 resulted in decreased GABPβ and BRCA1 expression in MCF-7 cells indicating that they form a transcriptional network. NRF-1 levels and activity did not differ between SK-BR-3 and MCF-7 cells, however the NRF-1 containing complex on the GABPβ promoter differed between the two lines and appears to be the result of altered coactivator binding. CONCLUSIONS: Both NRF-1 and GABP have been linked to the regulation of nuclear-encoded mitochondrial proteins, and the results of this study suggest their expression is coordinated by NRF-1's activation of the GABPβ promoter. Their linkage to BRCA1, a potential breast stem cell regulator, implies a connection between the induction of mitochondrial metabolism and breast differentiation.
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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 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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".