The Effect of tRNA<sup>[Ser]Sec</sup> Isopentenylation on Selenoprotein Expression
Transfer RNA<sup>[Ser]Sec</sup> carries multiple post-transcriptional modifications. The A37G mutation in tRNA<sup>[Ser]Sec</sup> abrogates isopentenylation of base 37 and has a profound effect on selenoprotein expression in mice. Patients with a homozygous pathogenic p.R323Q...
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| Autores principales: | , , , , , , , , , , , , , |
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| Formato: | article |
| Lenguaje: | EN |
| Publicado: |
MDPI AG
2021
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| Materias: | |
| Acceso en línea: | https://doaj.org/article/9a8205bba91f4fc3874f11f8544724c3 |
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| Sumario: | Transfer RNA<sup>[Ser]Sec</sup> carries multiple post-transcriptional modifications. The A37G mutation in tRNA<sup>[Ser]Sec</sup> abrogates isopentenylation of base 37 and has a profound effect on selenoprotein expression in mice. Patients with a homozygous pathogenic p.R323Q variant in tRNA-isopentenyl-transferase (<i>TRIT1</i>) show a severe neurological disorder, and hence we wondered whether selenoprotein expression was impaired. Patient fibroblasts with the homozygous p.R323Q variant did not show a general decrease in selenoprotein expression. However, recombinant human TRIT1<sup>R323Q</sup> had significantly diminished activities towards several tRNA substrates in vitro. We thus engineered mice conditionally deficient in <i>Trit1</i> in hepatocytes and neurons. Mass-spectrometry revealed that hypermodification of U<sub>34</sub> to mcm<sup>5</sup>Um occurs independently of isopentenylation of A<sub>37</sub> in tRNA<sup>[Ser]Sec</sup>. Western blotting and <sup>75</sup>Se metabolic labeling showed only moderate effects on selenoprotein levels and <sup>75</sup>Se incorporation. A detailed analysis of <i>Trit1</i>-deficient liver using ribosomal profiling demonstrated that UGA/Sec re-coding was moderately affected in <i>Selenop</i>, <i>Txnrd1</i>, and <i>Sephs2</i>, but not in <i>Gpx1</i>. 2′O-methylation of U<sub>34</sub> in tRNA<sup>[Ser]Sec</sup> depends on FTSJ1, but does not affect UGA/Sec re-coding in selenoprotein translation. Taken together, our results show that a lack of isopentenylation of tRNA<sup>[Ser]Sec</sup> affects UGA/Sec read-through but differs from a A37G mutation. |
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