Chapter 15 : Coronavirus Accessory Proteins

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Coronavirus Accessory Proteins, Page 1 of 2

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Coronaviruses are classified, based on comparative sequence analyses and other studies, into three major groups: 1, 2, and 3. The basic steps in the coronavirus replication cycle are conserved among several groups and are regulated by viral proteins encoded by a set of genes essential for viral replication and assembly. The essential genes include open reading frame 1ab (ORF 1ab), which occupies about two-thirds of the genome towards the 5’ end and encodes two large polyprotein precursors whose cleavage products are responsible for RNA replication and transcription. The other essential genes encode the common structural proteins, the spike protein (S protein), membrane protein (M protein), envelope protein (E protein), and nucleocapsid protein (N protein); these genes occupy the remaining one-third of the genome proximal to the 3’ end and are involved in infectious virus assembly. This chapter discusses current knowledge about the coronavirus accessory proteins to provide insight into the possible role of these proteins in the propagation of coronavirus under natural conditions. Group 1 coronaviruses have two or three accessory ORFs in the region between the S and E protein genes and two other ORFs 3’ to the N protein gene. The recent emergence of severe acute respiratory syndrome coronavirus (SARS-CoV) has led to further classification of group 2 into groups 2a and 2b. The prototypic group 3 avian coronavirus, infectious bronchitis virus (IBV) contains two group-specific genes, genes 3 and 5, which are functionally tricistronic and bicistronic, respectively.

Citation: Narayanan K, Huang C, Makino S. 2008. Coronavirus Accessory Proteins, p 235-244. In Perlman S, Gallagher T, Snijder E (ed), Nidoviruses. ASM Press, Washington, DC. doi: 10.1128/9781555815790.ch15

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Rift Valley fever virus
Severe Acute Respiratory Syndrome
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Figure 1.

Genome organization of the coronavirus accessory genes. The accessory genes are shown as gray boxes. One member of each group is shown as a representative example. The figure is not drawn to scale. RFS, ribosomal frameshift.

Citation: Narayanan K, Huang C, Makino S. 2008. Coronavirus Accessory Proteins, p 235-244. In Perlman S, Gallagher T, Snijder E (ed), Nidoviruses. ASM Press, Washington, DC. doi: 10.1128/9781555815790.ch15
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