Distinct 5′ UTR Requirements for Translation of the Bicistronic X/P mRNA Among Avian Orthobornaviruses
Bibliographic record
Abstract
Orthobornaviruses express X and the phosphoprotein (P) from a bicistronic X/P mRNA, and these proteins regulate polymerase activity. In mammalian orthobornaviruses, the 5' untranslated region (5' UTR) of the X/P mRNA controls the translational balance between X and P and thereby promotes efficient replication. Avian bornaviruses (ABVs) belong to two clades, clade-2 and -3, that differ in the structure and length of the 5' UTR of the X/P mRNA. However, the functional consequences of these differences remain unclear. Using reverse genetics, we generated chimeric viruses by reciprocally exchanging the 5' UTR of the X/P mRNA among clade 2 parrot bornavirus 5 (PaBV-5) and aquatic bird bornavirus 1 (ABBV-1) and clade 3 PaBV-4. In PaBV-5, a long 5' UTR with a stem-loop and an upstream ORF was required to maintain the X-to-P translational balance. On the other hand, replacing the 5' UTR of the X/P mRNA from PaBV-5 with that from PaBV-4 reduced X expression and markedly impaired viral growth. However, PaBV-4 tolerated the 5' UTR of the X/P mRNA from PaBV-5 without detectable effects on translation or replication, which suggests that translation of PaBV-4 X/P mRNA does not depend on the origin of the 5' UTR. Furthermore, ABBV-1 replicated efficiently with the 5' UTR of the X/P mRNA from PaBV-5 but was strongly attenuated with that from PaBV-4. Taken together, these results demonstrate a clade-dependent requirement for the 5' UTR for translation of the X/P mRNA and provide novel insights into the evolution of translational control in orthobornaviruses.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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) | 0.000 | 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 teacher head, 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".