Heterochromatin-dependent transcription links the PRC2 complex to small RNA-mediated DNA elimination
Bibliographic record
Abstract
Facultative heterochromatin is marked by the repressive histone modification H3K27me3 in eukaryotes. Deposited by the PRC2 complex, H3K27me3 is essential for regulating gene expression during development, and chromatin bearing this mark is generally considered transcriptionally inert. The PRC2 complex has also been linked to programmed DNA elimination during development in ciliates such as Paramecium. Due to a lack of mechanistic insight, a direct involvement has been questioned as most eliminated DNA segments in Paramecium are shorter than the size of a nucleosome. Here, we identify two sets of histone methylation readers essential for PRC2-mediated DNA elimination in Paramecium: Firefly1/2 and Mayfly1-4. The chromodomain proteins Firefly1/2 act in tight association with TFIIS4, a transcription elongation factor required for noncoding RNA transcription. These noncoding transcripts act as scaffolds for sequence-specific targeting by PIWI-bound sRNAs, resulting in local nucleosome depletion and DNA elimination. Our findings elucidate the molecular mechanism underlying the role of PRC2 in PIWI-mediated DNA elimination and suggest that its role in IES elimination may be to activate rather than repress transcription.
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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 | 0.000 | 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".