Crystal structures of the human histone H4K20 methyltransferases SUV420H1 and SUV420H2
Bibliographic record
Abstract
SUV420H1 and SUV420H2 are two highly homologous enzymes that methylate lysine 20 of histone H4 (H4K20), a mark that has been implicated in transcriptional regulation. In this study, we present the high-resolution crystal structures of human SUV420H1 and SUV420H2 in complex with SAM, and report their substrate specificity. Both methyltransferases have a unique N-terminal domain and Zn-binding post-SET domain, and prefer the monomethylated histone H4K20 as a substrate in vitro. No histone H4K20 trimethylation activity was detected by our radioactivity-based assay for either enzyme, consistent with the presence of a conserved serine residue that forms a hydrogen bond with the target lysine side-chain and limits the methylation level.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.002 |
| Insufficient payload (model declined to judge) | 0.003 | 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".