Aberrant Double-Strand Break Repair Resulting in Half Crossovers in Mutants Defective for Rad51 or the DNA Polymerase δ Complex
Bibliographic record
Abstract
Homologous recombination is an error-free mechanism for the repair of DNA double-strand breaks (DSBs). Most DSB repair events occur by gene conversion limiting loss of heterozygosity (LOH) for markers downstream of the site of repair and restricting deleterious chromosome rearrangements. DSBs with only one end available for repair undergo strand invasion into a homologous duplex DNA, followed by replication to the chromosome end (break-induced replication [BIR]), leading to LOH for all markers downstream of the site of strand invasion. Using a transformation-based assay system, we show that most of the apparent BIR events that arise in diploid Saccharomyces cerevisiae rad51Delta mutants are due to half crossovers instead of BIR. These events lead to extensive LOH because one arm of chromosome III is deleted. This outcome is also observed in pol32Delta and pol3-ct mutants, defective for components of the DNA polymerase delta (Pol delta) complex. The half crossovers formed in Pol delta complex mutants show evidence of limited homology-dependent DNA synthesis and are partially Mus81 dependent, suggesting that strand invasion occurs and the stalled intermediate is subsequently cleaved. In contrast to rad51Delta mutants, the Pol delta complex mutants are proficient for repair of a 238-bp gap by gene conversion. Thus, the BIR defect observed for rad51 mutants is due to strand invasion failure, whereas the Pol delta complex mutants are proficient for strand invasion but unable to complete extensive tracts of recombination-initiated DNA synthesis.
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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) | 0.001 | 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".