A Role for the Drosophila SU(VAR)3-9 Protein in Chromatin Organization at the Histone Gene Cluster and in Suppression of Position-Effect Variegation
Bibliographic record
Abstract
Mutations in the gene for Su(var)3-9 are dominant suppressors of position-effect variegation (PEV). We show that SU(VAR)3-9 is a chromatin-associated protein and identify the large multicopy histone gene cluster (HIS-C) as one of its target loci. The organization of nucleosomes over the entire HIS-C region is altered in Su(var)3-9 mutants and there is a concomitant increase in expression of the histone genes. SU(VAR)3-9 is a histone H3 methyltransferase and, using chromatin immunoprecipitation, we show that SU(VAR)3-9 is present at the HIS-C locus and that the histone H3 at the HIS-C locus is methylated. We propose that SU(VAR)3-9 is involved in packaging HIS-C into a distinct chromatin domain that has some of the characteristics of beta-heterochromatin. We suggest that methylation of histone H3 is important for the chromatin structure at HIS-C. The chromosomal deficiency for the HIS-C is also a suppressor of PEV. In contrast to what might be expected, we show that hemizygosity for the HIS-C locus leads to a substantial increase in the histone transcripts.
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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".