Disruption of host selenobiology by SARS-CoV-2 and Ebola virus via RNA:RNA antisense interactions

UNCG Author/Contributor (non-UNCG co-authors, if there are any, appear on document)
David B. Stubbs (Creator)
The University of North Carolina at Greensboro (UNCG )
Web Site: http://library.uncg.edu/
Ethan Taylor

Abstract: Selenium is an essential, but often overlooked, element in maintaining the health of our biological systems. Occupying the redox center of different selenoproteins, such as thioredoxin reductase (TXNRD) or glutathione peroxidase as selenocysteine (SeC), allows them to perform various unique biological functions, e.g., redox regulation and antioxidant defense. The synthesis of selenoproteins involves the reprogramming of a UGA stop codon to allow the recruitment of a SeC t-RNA. This occurs during translation, using a unique RNA structure called a selenocysteine insertion sequence (SECIS) element. The SECIS element can be located within the mRNA being translated but can also be hijacked from a second RNA molecule through antisense tethering. This tethering can also facilitate another translation event in the form of ribosomal frameshifting that allows genes to encode for multiple proteins by overlapping reading frames. Our research group has previously identified such frameshift sites in several pathogenic RNA viruses, including Ebola virus (EBOV) and HIV-1. This antisense tethering could enhance the frameshifting event to allow the recoding of those UGA codons as SeC. Evidence will be presented for these events being programmed in the genomes of EBOV and SARS-CoV-2. The EBOV nucleoprotein gene is an example of the reprogramming of a UGA stop codon as a potential SeC codon. Using green fluorescent protein as a downstream reporter gene, we show selenium-dependent read-through of the 3’-UGA stop codon, which is highly conserved only in the most virulent strains of EBOV. In the EBOV polymerase (L) gene, a programmed ribosomal frameshift signal leads to an overlapping gene with 2 tandem UGA codons immediately followed by an RNA region that is the inverse complement (antisense) to a region of the selenoprotein iodothyronine deiodinase II (DIO2) mRNA, which could both trigger the ribosomal frameshift and provide access to the SECIS element contained in the DIO2 mRNA. We have designed an innovative assay for -1 frameshifting at such sites in which upstream and downstream reporter genes are used to assess the initiation and termination of protein synthesis. By inserting a wildtype or mutant viral insert, we show a highly significant level of -1 ribosomal frameshifting at the EBOV L gene site mentioned above. In SARS-CoV-2, we have demonstrated an antisense interaction between a region of the viral RNA and the mRNA for TXNRD3, another selenoprotein that is highly expressed in the human testes. This predicted antisense interaction was confirmed experimentally by knockdown of TXNRD3 mRNA in SARS-CoV-2 infected Vero cells. The significance of these findings regarding links between selenium status and the severity of Covid-19, and EBOV infection, will be discussed.

Additional Information

Language: English
Date: 2023
Antisense Tethering, Frameshifting, Selenium, Stop Codon Read Through, Virology
COVID-19 (Disease)
Ebola virus disease
Antisense RNA

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