The addition of a methyl group to the N6-position of adenosine (m
A) is considered one of the most prevalent internal post-transcriptional modifications and is attributed to virus replication and ...cell biology. Viral epitranscriptome sequencing analysis has revealed that hemagglutinin (HA) mRNA of H1N1 carry eight m
A sites which are primarily enriched in 5'-DRACH-3' sequence motif. Herein, a large-scale comparative m
A analysis was conducted to investigate the conservation patterns of the DRACH motifs that corresponding to the reference m
A sites among influenza A viruses. A total of 70,030 complete HA sequences that comprise all known HA subtypes (H1-18) collected over several years, countries, and affected host species were analysed on both mRNA and vRNA strands. The bioinformatic analysis revealed the highest degree of DRACHs conservation among all H1 sequences that clustered largely in the middle and in the vicinity to 3' end with at least four DRACH motifs were conserved in all mRNA sequences. The major HA-containing subtypes displayed a modest DRACH motif conservation located either in the middle region of HA transcript (H3) or at the 3' end (H5) or were distributed across the length of HA sequence (H9). The lowest conservation was demonstrated in HA subtypes that infect mostly the wild type avian species and bats. Interestingly, the total number and the conserved DRACH motifs in the vRNA were found to be much lower than those observed in the mRNA. Collectively, the identification of putative m
A topology provides a foundation for the future intervention of influenza infection, replication, and pathobiology in susceptible hosts.
Prokaryotes have evolutionarily acquired an immune system to fend off invading mobile genetic elements, including viral phages and plasmids. Through recognizing specific sequences of the invading ...nucleic acid, prokaryotes mediate a subsequent degradation process collectively referred to as the Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-CRISPR-associated (Cas) (CRISPR-Cas) system. The CRISPR-Cas systems are divided into two main classes depending on the structure of the effector Cas proteins. Class I systems have effector modules consisting of multiple proteins, while class II systems have a single multidomain effector. Additionally, the CRISPR-Cas systems can also be categorized into types depending on the spacer acquisition components and their evolutionary features, namely, types I-VI. Among CRISPR/Cas systems, Cas9 is one of the most common multidomain nucleases that identify, degrade, and modulate DNA. Importantly, variants of Cas proteins have recently been found to target RNA, especially the single-effector Cas13 nucleases. The Cas13 has revolutionized our ability to study and perturb RNAs in endogenous microenvironments. The Cas13 effectors offer an excellent candidate for developing novel research tools in virological and biotechnological fields. Herein, in this review, we aim to provide a comprehensive summary of the recent advances of Cas13s for targeting viral RNA for either RNA-mediated degradation or CRISPR-Cas13-based diagnostics. Additionally, we aim to provide an overview of the proposed applications that could revolutionize our understanding of viral-host interactions using Cas13-mediated approaches.
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