Coronaviruses (CoVs), enveloped positive-sense RNA viruses, are characterized by club-like spikes that project from their surface, an unusually large RNA genome, and a unique replication strategy. Coronaviruses cause a variety of diseases in mammals and birds ranging from enteritis in cows and pigs and upper respiratory disease in chickens to potentially lethal human respiratory infections. Here we provide a brief introduction to coronaviruses discussing their replication and pathogenicity, and current prevention and treatment strategies. We also discuss the outbreaks of the highly pathogenic Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV) and the recently identified Middle Eastern Respiratory Syndrome Coronavirus (MERS-CoV).

/pdf/coronaviruses-an-overview-of-their-replication-and-4lyvr9vdqs.pdf

Coronaviruses: An Overview of Their Replication and Pathogenesis

The recent emergence of a novel coronavirus (2019-nCoV), which is causing an outbreak of unusual viral pneumonia in patients in Wuhan, a central city in China, is another warning of the risk of CoVs posed to public health. In this minireview, we provide a brief introduction of the general features of CoVs and describe diseases caused by different CoVs in humans and animals. This review will help understand the biology and potential risk of CoVs that exist in richness in wildlife such as bats.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/jmv.25681

Emerging coronaviruses: Genome structure, replication, and pathogenesis.

The SARS-CoV-2 pandemic and its unprecedented global societal and economic disruptive impact has marked the third zoonotic introduction of a highly pathogenic coronavirus into the human population. Although the previous coronavirus SARS-CoV and MERS-CoV epidemics raised awareness of the need for clinically available therapeutic or preventive interventions, to date, no treatments with proven efficacy are available. The development of effective intervention strategies relies on the knowledge of molecular and cellular mechanisms of coronavirus infections, which highlights the significance of studying virus-host interactions at the molecular level to identify targets for antiviral intervention and to elucidate critical viral and host determinants that are decisive for the development of severe disease. In this Review, we summarize the first discoveries that shape our current understanding of SARS-CoV-2 infection throughout the intracellular viral life cycle and relate that to our knowledge of coronavirus biology. The elucidation of similarities and differences between SARS-CoV-2 and other coronaviruses will support future preparedness and strategies to combat coronavirus infections.

/pdf/coronavirus-biology-and-replication-implications-for-sars-47nwmem9di.pdf

Coronavirus biology and replication: implications for SARS-CoV-2.

Although coronaviruses were first identified nearly 60 years ago, they only received notoriety in 2003 when one of their members was identified as the aetiological agent of severe acute respiratory syndrome. Previously these viruses were known to be important agents of respiratory and enteric infections of domestic and companion animals and to cause approximately 15% of all cases of the common cold. This Review focuses on recent advances in our understanding of the mechanisms of coronavirus replication, interactions with the host immune response and disease pathogenesis. It also highlights the recent identification of numerous novel coronaviruses and the propensity of this virus family to cross species barriers.

/pdf/coronaviruses-post-sars-update-on-replication-and-1kt8r3mwyy.pdf

Coronaviruses post-SARS: update on replication and pathogenesis.

Immunology of COVID-19: Current State of the Science.

The N7-methylguanosine (m7G) cap is the defining structural feature of eukaryotic mRNAs. Most eukaryotic viruses that replicate in the cytoplasm, including coronaviruses, have evolved strategies to cap their RNAs. In this report, we used a yeast genetic system to functionally screen for the cap-forming enzymes encoded by severe acute respiratory syndrome (SARS) coronavirus and identified the nonstructural protein (nsp) 14 of SARS coronavirus as a (guanine-N7)-methyltransferase (N7-MTase) in vivo in yeast cells and in vitro using purified enzymes and RNA substrates. Interestingly, coronavirus nsp14 was previously characterized as a 3'-to-5' exoribonuclease, and by mutational analysis, we mapped the N7-MTase domain to the carboxy-terminal part of nsp14 that shows features conserved with cellular N7-MTase in structure-based sequence alignment. The exoribonuclease active site was dispensable but the exoribonuclease domain was required for N7-MTase activity. Such combination of the 2 functional domains in coronavirus nsp14 suggests that it may represent a novel form of RNA-processing enzymes. Mutational analysis in a replicon system showed that the N7-MTase activity was important for SARS virus replication/transcription and can thus be used as an attractive drug target to develop antivirals for control of coronaviruses including the deadly SARS virus. Furthermore, the observation that the N7-MTase of RNA life could function in lieu of that in DNA life provides interesting evolutionary insight and practical possibilities in antiviral drug screening.

https://www.pnas.org/content/pnas/early/2009/02/10/0808790106.full.pdf

Functional screen reveals SARS coronavirus nonstructural protein nsp14 as a novel cap N7 methyltransferase

Coronaviruses possess a cap structure at the 5' ends of viral genomic RNA and subgenomic RNAs, which is generated through consecutive methylations by virally encoded guanine-N7-methyltransferase (N7-MTase) and 2'-O-methyltransferase (2'-O-MTase). The coronaviral N7-MTase is unique for its physical linkage with an exoribonuclease (ExoN) harbored in nonstructural protein 14 (nsp14) of coronaviruses. In this study, the structure-function relationships of the N7-MTase were analyzed by deletion and site-directed mutagenesis of severe acute respiratory syndrome coronavirus (SARS-CoV) nsp14. The results showed that the ExoN domain is closely involved in the activity of the N7-MTase, suggesting that coronavirus N7-MTase is different from all other viral N7-MTases, which are separable from other structural domains located in the same polypeptide. Two of the 12 critical residues identified to be essential for the N7-MTase were located at the N terminus of the core ExoN domain, reinforcing a role of the ExoN domain in the N7-MTase activity of nsp14. The other 10 critical residues were distributed throughout the N7-MTase domain but localized mainly in the S-adenosyl-l-methionine (SAM)-binding pocket and key structural elements of the MTase fold of nsp14. The sequence motif DxGxPxA (amino acids [aa] 331 to 338) was identified as the key part of the SAM-binding site. These results provide insights into the structure and functional mechanisms of coronaviral nsp14 N7-MTase.

/pdf/structure-function-analysis-of-severe-acute-respiratory-32xemp671q.pdf

Structure-Function Analysis of Severe Acute Respiratory Syndrome Coronavirus RNA Cap Guanine-N7-Methyltransferase

In this study, two H5N1 influenza viruses (HN021 and HN211) were isolated in wild ducks and the characteristics of these viruses were studied systemically. By studying the pathogenesis of both H5N1 isolates, the results showed that HN211 was highly pathogenic in chickens, geese, ducks, and mice, while HN021 was highly pathogenic in chickens and geese but low pathogenic in ducks and mice. Both isolates could replicate in lungs and brains of mice and be transmitted from ducks to ducks. Histopathologic analysis showed that HN211 could cause more severe pathological changes in lungs and brains of infected mice than HN021. Molecular characterization showed that both H5N1 isolates had 20 aa missing in stalk of NA protein and 5 aa missing in NS protein in comparison with most other H5N1 isolates. Phylogenetic analysis indicated that both H5N1 isolates were reassortants from Goose/Guangdong/1/96-like viruses. The results of present study with both H5N1 viruses also suggested that wild ducks may play an important role in maintaining circulation of H5N1 viruses.

https://link.springer.com/content/pdf/10.1007%2Fs11262-008-0245-x.pdf

Hui Cai

Papers

Functional screen reveals SARS coronavirus nonstructural protein nsp14 as a novel cap N7 methyltransferase

Structure-Function Analysis of Severe Acute Respiratory Syndrome Coronavirus RNA Cap Guanine-N7-Methyltransferase

Molecular and pathological characterization of two H5N1 avian influenza viruses isolated from wild ducks

RNA Cap Guanine-N7-Methyltransferase Acute Respiratory Syndrome Coronavirus Structure-Function Analysis of Severe