Hendrick, A. | Search bioRxiv

bioRxiv2023

Pseudouridine guides germline small RNA transport and epigenetic inheritance

Epigenetic modifications that arise during plant and animal development, such as DNA and histone modification, are mostly reset during gamete formation, but some are inherited from the germline including those marking imprinted genes1. Small RNAs guide these epigenetic modifications, and some are also inherited by the next generation2,3. In C. elegans, these inherited small RNAs have poly (UG) tails4, but how inherited small RNAs are distinguished in other animals and plants is unknown. Pseudouridine ({Psi}) is the most abundant RNA modification but has not been explored in small RNAs. Here, we develop novel assays to detect {Psi} in short RNA sequences, demonstrating its presence in mouse and Arabidopsis microRNAs and their precursors. We also detect substantial enrichment in germline small RNAs, namely epigenetically activated siRNAs (easiRNAs) in Arabidopsis pollen, and piwi-interacting piRNAs in mouse testis. In pollen, pseudouridylated easiRNAs are localized to sperm cells, and we found that PAUSED/HEN5 (PSD), the plant homolog of Exportin-t, interacts genetically with {Psi} and is required for transport of easiRNAs into sperm cells from the vegetative nucleus. We further show that Exportin-t is required for the triploid block: chromosome dosage-dependent seed lethality that is epigenetically inherited from pollen. Thus, {Psi} has a conserved role in marking inherited small RNAs in the germline. One-Sentence SummaryPseudouridine marks germline small RNAs in plants and mammals, impacting epigenetic inheritance via nuclear transport.

genetics↗

bioRxiv2020

Translational adaptation to heat stress is mediated by 5-methylcytosine RNA modification in Caenorhabditis elegans

Methylation of carbon-5 of cytosines (m5C) is a post-transcriptional nucleotide modification of RNA found in all kingdoms of life. While individual m5C-methyltransferases have been studied, the impact of the global cytosine-5 methylome on development, homeostasis and stress remains unknown. Here, using Caenorhabditis elegans, we generated the first organism devoid of m5C in RNA, demonstrating that this modification is non-essential. We determined the localisation and enzymatic specificity of m5C sites in RNA in vivo and showed that animals devoid of m5C are sensitive to temperature stress. At the molecular level, we showed that loss of m5C specifically impacts decoding of leucine and proline thus reducing the translation efficiency of transcripts enriched in these amino acids. Finally, we found translation of leucine UUG codons to be the most strongly affected upon heat shock, suggesting a role of m5C tRNA wobble methylation in the adaptation to heat stress.

genetics↗