Grondin, B. | bioRxiv Science

bioRxiv2024

The dual coding gene SLC35A4 protects against oxidative stress

Alternative proteins (AltProts) represent a newly recognized class of biologically active proteins encoded from alternative open reading frames (AltORFs) within already annotated genes. This study focuses on the SLC35A4 gene, which encodes both the reference protein SLC35A4 and the alternative protein AltSLC35A4. Using a combination of microscopy and biochemical analyses, we confirmed the presence of AltSLC35A4 in the inner mitochondrial membrane, resolving previous conflicting reports. Previous studies employing ribosome profiling have revealed that during oxidative stress induced by sodium arsenite, the reference coding sequence of SLC35A4 exhibits the largest increase in translational efficiency among all cellular mRNAs. Our results confirmed this translational upregulation, with the emergence of SLC35A4 protein isoforms during oxidative stress in an upstream ORF-dependent manner. Notably, the expression of AltSLC35A4 remained unchanged during oxidative stress. Knock- out of SLC35A4 enhanced sensitivity to oxidative stress in a rescuable manner, indicating a direct implication for SLC35A4 in stress resistance. In conclusion, our research provides compelling evidence for the functional significance of the dual-coding nature of SLC35A4 for resistance to oxidative stress and highlights the importance of considering AltProts in the functional study of eukaryotic genes.

cell biology↗

bioRxiv2022

FAM172A controls the nuclear import and alternative splicing function of AGO2

The poorly characterized protein FAM172A is mutated in some individuals affected by a disorder of neural crest development called CHARGE syndrome. We also know that FAM172A can interact with the main CHARGE syndrome-associated protein CHD7 and the small RNA-binding protein AGO2 at the chromatin-spliceosome interface. Focusing on this intriguing FAM172A-AGO2 interaction, we now report that FAM172A is one of the long sought-after regulator of AGO2 nuclear import. This FAM172A function relies on its nuclear localization signal, being enhanced by CK2-mediated phosphorylation and abrogated by a CHARGE syndrome-associated missense mutation. Accordingly, Fam172a and Ago2 genetically interact in mice, and neural crest-specific depletion of Ago2 is sufficient to phenocopy CHARGE syndrome without impacting post-transcriptional gene silencing. Rapamycin-mediated rescue suggests that observed morphological anomalies are instead due to alternative splicing defects. This work thus demonstrates that non-canonical nuclear functions of AGO2 and associated regulatory mechanisms may be clinically relevant.

developmental biology↗