The nuclear tRNA aminoacylation-dependent pathway may be the principal route used to export tRNA from the nucleus in Saccharomyces cerevisiae
Bibliographic record
Abstract
Nuclear tRNA export in Saccharomyces cerevisiae has been proposed to involve three pathways, designated Los1p-dependent, Los1p-independent nuclear aminoacylation-dependent, and Los1p- and nuclear aminoacylation-independent. Here, a comprehensive biochemical analysis was performed to identify tRNAs exported by the aminoacylation-dependent and -independent pathways of S. cerevisiae. Interestingly, the major tRNA species of at least 19 families were found in the aminoacylated form in the nucleus. tRNAs known to be exported by the export receptor Los1p were also aminoacylated in the nucleus of both wild-type and mutant Los1p strains. FISH (fluorescence in situ hybridization) analyses showed that tRNA(Tyr) co-localizes with the U18 small nucleolar RNA in the nucleolus of a tyrosyl-tRNA synthetase mutant strain defective in nuclear tRNA(Tyr) export because of a block in nuclear tRNA(Tyr) aminoacylation. tRNA(Tyr) was also found in the nucleolus of a utp8 mutant strain defective in nuclear tRNA export but not nuclear tRNA aminoacylation. These results strongly suggest that the nuclear aminoacylation-dependent pathway is principally responsible for tRNA export in S. cerevisiae and that Los1p is an export receptor of this pathway. It is also likely that in mammalian cells tRNAs are mainly exported from the nucleus by the nuclear aminoacylation-dependent pathway. In addition, the data are consistent with the idea that nuclear aminoacylation is used as a quality control mechanism for ensuring nuclear export of only mature and functional tRNAs, and that this quality assurance step occurs in the nucleolus.
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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 | 0.000 |
| 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".