Poster abstracts
Poster number 10 submitted by Cameron Divoky
Biogenesis of Human Tiny RNAs and their Link to Disease
Cameron Divoky (Ohio State University), GeunYoung Sim (Ohio State University), Audrey Kehling (Ohio State University), Kotaro Nakanishi (Ohio State University)
Abstract:
MicroRNAs (miRNAs) and Argonaute (AGO) proteins form complexes called RNA-induced silencing complexes (RISCs) that are responsible for the regulation of eukaryotic mRNAs. miRNAs are loaded into one of the four AGOs (AGO1-4) as a duplex where one strand is retained as a guide while the other is ejected from the complex1. Once the RISC is formed, the guide is used to repress complimentary mRNAs through the recruitment of accessory proteins or by directly slicing the mRNA. AGO2 was traditionally thought to be the only human AGO paralog capable of slicing a mRNA, but our lab discovered that AGO3 was also able to slice when loaded with the appropriate miRNA. Interestingly, slicing by AGO3 drastically increased with 14~15-nt guides compared to their full-length counterparts2. We termed these shortened miRNAs, tiny RNAs (tyRNAs) and have since sought to uncover their biogenesis using both in vitro and in vivo assays. We have identified three exonucleases capable of converting AGO-bound miRNAs into tyRNAs; 3’ Repair Exonuclease 1 (TREX1), Enhanced RNAi 1 (ERI1) , and Interferon Stimulated Gene 20 kDa (ISG20), with the most potent being ISG20. While ERI1 and TREX1 are expressed continuously in humans, ISG20 is only expressed during the interferon response and upon stress conditions, suggesting that the RNAi machinery may be modified because of those specific conditions or diseases3. Further experiments using AGO1 mutants linked to neurodevelopmental diseases lead to the discovery that tyRNAs were generated at equal rates to the wild-type but displayed unique band patterns. Taken together, these results suggest that the generation of tyRNA in humans is a key step in the dysregulation of gene regulation.
References:
1. Nakanishi Anatomy of four human Argonaute proteins. Nucleic Acids Res. (2022)
2. Park et al., Human Argonaute2 and Argonaute3 are catalytically activated by different lengths of guide RNA. PNAS (2020).
3. Sim et al., Manganese-dependent microRNA trimming by 3′→ 5′ exonucleases generates 14-nucleotide or shorter tiny RNAs. PNAS (2022).
Keywords: miRNA, tyRNA, RNAi