Evolution of the Eukaryotic Translation Termination System: Origins of Release Factors
Bibliographic record
Abstract
Accurate translation termination is essential for cell viability. In eukaryotes, this process is strictly maintained by two proteins, eukaryotic release factor 1 (eRF1), which recognizes all stop codons and hydrolyzes peptidyl-tRNA, and eukaryotic release factor 3 (eRF3), which is an elongation factor 1alpha (EF-1alpha) homolog stimulating eRF1 activity. To retrace the evolution of this core system, we cloned and sequenced the eRF3 genes from Trichomonas vaginalis (Parabasalia) and Giardia lamblia (Diplomonada), which are generally thought to be "early-diverging eukaryotes," as well as those from two ciliates (Oxytricha trifallax and Euplotes aediculatus). We also determined the sequence of the eRF1 gene for G. lamblia. Surprisingly, the G. lamblia eRF3 appears to have only one domain, corresponding to EF-1alpha, while other eRF3s (including the T. vaginalis protein) have an additional N-terminal domain, of 66-411 amino acids. Considering this novel eRF3 structure and our extensive phylogenetic analyses, we suggest that (1) the current translation termination system in eukaryotes evolved from the archaea-like version, (2) eRF3 was introduced into the system prior to the divergence of extant eukaryotes, including G. lamblia, and (3) G. lamblia might be the first eukaryotic branch among the organisms considered.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 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".