Poly(ADP-ribosyl)ation-dependent Transient Chromatin Decondensation and Histone Displacement following Laser Microirradiation
Bibliographic record
Abstract
Chromatin undergoes a rapid ATP-dependent, ATM and H2AX-independent decondensation when DNA damage is introduced by laser microirradiation. Although the detailed mechanism of this decondensation remains to be determined, the kinetics of decondensation are similar to the kinetics of poly(ADP-ribosyl)ation. We used laser microirradiation to introduce DNA strand breaks into living cells expressing a photoactivatable GFP-tagged histone H2B. We find that poly(ADP-ribosyl)ation mediated primarily by poly(ADP-ribose) polymerase 1 (PARP1) is responsible for the rapid decondensation of chromatin at sites of DNA damage. This decondensation of chromatin correlates temporally with the displacement of histones, which is sensitive to PARP inhibition and is transient in nature. Contrary to the predictions of the histone shuttle hypothesis, we did not find that histone H1 accumulated on poly(ADP-ribose) (PAR) in vivo. Rather, histone H1, and to a lessor extent, histones H2A and H2B were rapidly depleted from the sites of PAR accumulation. However, histone H1 returns to chromatin and the chromatin recondenses. Thus, the PARP-dependent relaxation of chromatin closely correlates with histone displacement.
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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 | 0.000 |
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".