Publicação
Impact of tRNA modifications and translation control for pathogenicity and host responses upon influenza A virus infection
| Resumo: | Viruses rely heavily on the host cell translation machinery, including host transfer RNAs (tRNAs), to efficiently translate their genomes. However, many viral RNA genomes, including the influenza A virus (IAV), are enriched in codons ending in adenine (A) or uridine (U), whereas the human genome is rich in cytosine (C) or guanine (G) ending codons. This is a challenge for viruses, as they require decoding of sub-optimal codons for which cognate host tRNAs are underrepresented. Nevertheless, despite the codon usage differences, codon-biased translation of IAV genes is highly efficient, suggesting the existence of viral strategies to manipulate host tRNA populations for optimal viral protein production. The reprogramming of host cell tRNA modifications upon infection may be one such strategy. tRNAs harbor a plethora of chemical modifications, collectively known as the tRNA epitranscriptome. These modifications are catalyzed by different classes of tRNA-modifying enzymes and, when they occur in the anticodon loop region, ensure the efficiency and fidelity of the translation process. These epitranscriptomic marks exhibit a dynamic behavior across cells and tissues, changing rapidly in response to environmental cues to maximize translation of stress-response genes. Given that viruses are sources of host cellular stress, it is possible that modulation of the hosts’ tRNA epitranscriptome occurs in this context. In this dissertation, I set to explore if and how host cell tRNA modifications were remodeled in a single cycle of IAV infection. The obtained results demonstrate that IAV infection affects the levels of mcm5U34 and mcm5s2U34 and of cognate tRNA modifying enzymes, including the elongator acetyltransferase complex subunit 3 (ELP3). To evaluate the relevance of ELP3 and its dependent modifications in the context of IAV infection, knockdown experiments were conducted. Loss of ELP3 induced tRNA hypomodifications and impaired translation of codon biased IAV genes. Moreover, the ELP3 knockdown triggered the integrated stress response (ISR) and interfered with the unfolded protein response (UPR)-related mechanisms, pivotal for IAV propagation. Specifically, silencing of ELP3 prior to IAV infection intensified the phosphorylation of the eukaryotic initiation factor 2 (eIF2α) and inhibited the inositol-requiring enzyme 1 α (IRE1α) axis concomitant to the accumulation of protein aggregates in the endoplasmic reticulum (ER) lumen of host-infected cells. Ultimately, induction of eIF2α likely amplified host antiviral responses linked to the NF-kB pathway, promoting the expression of interferon beta (IFN-β) and IFN regulatory factor 1 (IRF1). Taken together, our results uncover the relevance of the host cell tRNA epitranscriptome for optimal expression of viral genomes and host antiviral responses, setting the tRNA epitranscriptome as a promising host-based antiviral target. |
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| Autores principais: | Ribeiro, Diana Roberta da Cruz |
| Assunto: | Transfer RNAs Epitranscriptome tRNA-modifying enzymes ELP3 Codon usage RNA viruses Influenza A virus Antiviral response |
| Ano: | 2024 |
| País: | Portugal |
| Tipo de documento: | tese de doutoramento |
| Tipo de acesso: | acesso embargado |
| Instituição associada: | Universidade de Aveiro |
| Idioma: | inglês |
| Origem: | RIA - Repositório Institucional da Universidade de Aveiro |
| Resumo: | Viruses rely heavily on the host cell translation machinery, including host transfer RNAs (tRNAs), to efficiently translate their genomes. However, many viral RNA genomes, including the influenza A virus (IAV), are enriched in codons ending in adenine (A) or uridine (U), whereas the human genome is rich in cytosine (C) or guanine (G) ending codons. This is a challenge for viruses, as they require decoding of sub-optimal codons for which cognate host tRNAs are underrepresented. Nevertheless, despite the codon usage differences, codon-biased translation of IAV genes is highly efficient, suggesting the existence of viral strategies to manipulate host tRNA populations for optimal viral protein production. The reprogramming of host cell tRNA modifications upon infection may be one such strategy. tRNAs harbor a plethora of chemical modifications, collectively known as the tRNA epitranscriptome. These modifications are catalyzed by different classes of tRNA-modifying enzymes and, when they occur in the anticodon loop region, ensure the efficiency and fidelity of the translation process. These epitranscriptomic marks exhibit a dynamic behavior across cells and tissues, changing rapidly in response to environmental cues to maximize translation of stress-response genes. Given that viruses are sources of host cellular stress, it is possible that modulation of the hosts’ tRNA epitranscriptome occurs in this context. In this dissertation, I set to explore if and how host cell tRNA modifications were remodeled in a single cycle of IAV infection. The obtained results demonstrate that IAV infection affects the levels of mcm5U34 and mcm5s2U34 and of cognate tRNA modifying enzymes, including the elongator acetyltransferase complex subunit 3 (ELP3). To evaluate the relevance of ELP3 and its dependent modifications in the context of IAV infection, knockdown experiments were conducted. Loss of ELP3 induced tRNA hypomodifications and impaired translation of codon biased IAV genes. Moreover, the ELP3 knockdown triggered the integrated stress response (ISR) and interfered with the unfolded protein response (UPR)-related mechanisms, pivotal for IAV propagation. Specifically, silencing of ELP3 prior to IAV infection intensified the phosphorylation of the eukaryotic initiation factor 2 (eIF2α) and inhibited the inositol-requiring enzyme 1 α (IRE1α) axis concomitant to the accumulation of protein aggregates in the endoplasmic reticulum (ER) lumen of host-infected cells. Ultimately, induction of eIF2α likely amplified host antiviral responses linked to the NF-kB pathway, promoting the expression of interferon beta (IFN-β) and IFN regulatory factor 1 (IRF1). Taken together, our results uncover the relevance of the host cell tRNA epitranscriptome for optimal expression of viral genomes and host antiviral responses, setting the tRNA epitranscriptome as a promising host-based antiviral target. |
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