The RNA demethylases ALKBH5 and FTO regulate translation of the ATF4 mRNA in sorafenib-treated hepatocarcinoma cells
Bibliographic record
Abstract
Abstract Translation is one of the main gene expression steps targeted by cellular stress, commonly refereed as translational stress, which includes treatment with anticancer drugs. While translational stress blocks translation initiation of bulk mRNAs, it allows translation of a specific set of mRNAs known as short upstream open reading frames (uORFs)-mRNAs. Among these, ATF4 mRNA encodes a transcription factor that reprograms gene expression during various cellular stress towards functions required for cell response to stress. Stress-induced ATF4 mRNA translation occurs via a specialised mode that relies on the presence of uORFs upstream to the main ATF4 ORF. However, mechanisms regulating ATF4 mRNA translation, particularly towards chemoresistance, remained limited. Here, we report a role of both ALKBH5 and FTO, the two RNA demethylating enzymes in promoting translation of ATF4 mRNA in liver cancer Hep3B cells treated with sorafenib, a stress inducer used in chemotherapy. Depletion experiments confirmed that both enzymes are required for inducing ATF4 mRNA translation, while polyribosome assays coupled to RT-qPCR indicated that this induction of ATF4 mRNA translation occurs at its initiation step. Using in vitro methylation assays, we found that ALKBH5 is required for the inhibition of the methylation of a reporter ATF4 mRNA at a conserved adenosine (A235) site located at its uORF2, suggesting that ALKBH5-mediated translation of ATF4 mRNA involves demethylation of its A235. Preventing methylation of A235 by introducing an A/G mutation into the ATF4 mRNA reporter renders that reporter insensitive to ALKBH5 depletion, supporting the role of ALKBH5 demethylation activity in translation. Finally, targeting either ALKBH5 or FTO sensitizes Hep3B to sorafenib-induced cell death, contributing to their resistance. We concluded that ALKBH5 and FTO are novel factors that promote resistance to sorafenib treatment, in part by mediating translation of ATF4 mRNA.
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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".