Biochemical Analysis of Transcriptional Repression byDrosophila Histone Deacetylase 1
Bibliographic record
Abstract
To study the mechanisms by which deacetylases regulate transcription by RNA polymerase II, we investigated the biochemical properties of purified recombinant Drosophila histone deacetylase 1 (dHDAC1, also known as dRPD3). We found that purified dHDAC1 and Gal4-dHDAC1 polypeptides possess substantial deacetylase activity. Thus, deacetylation by dHDAC1 does not require any additional cofactors. Gal4-dHDAC1, but not dHDAC1, was observed to repress transcription in vitro by about 2-3-fold from chromatin templates, but not from naked DNA templates, in a Gal4 site-dependent manner. This magnitude of repression is similar to that commonly seen by deacetylases in vivo, as assessed by treatment of cells with deacetylase inhibitors. Transcriptional repression by Gal4-dHDAC1 was blocked by the deacetylase inhibitor, FR901228, and thus, deacetylase activity correlates with repression. Single round transcription analyses showed that Gal4-dHDAC1 reduces the absolute number of productive initiation complexes with chromatin templates. Moreover, with chromatin templates that were assembled with completely purified components, Gal4-dHDAC1 was found to deacetylate nucleosomal histones as well as to repress transcription. These experiments provide biochemical evidence for the requirement of chromatin for transcriptional repression by dHDAC1 and further show that dHDAC1 acts to repress the transcription initiation process.
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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 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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 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".