Accessory proteins of SARS-CoV and other coronaviruses

•The SARS-CoV genome encodes eight accessory proteins; none is essential for RNA replication.•Several appear to be involved in virus–host interactions and to influence the pathogenicity of the virus.•Some of these accessory proteins modulate the interferon pathway and the production of pro-inflammatory cytokines.•Five of the accessory proteins are incorporated into virions as minor structural proteins.•Other coronaviruses including MERS-CoV also encode accessory proteins. The huge RNA genome of SARS coronavirus comprises a number of open reading frames that code for a total of eight accessory proteins. Although none of these are essential for virus replication, some appear to have a role in virus pathogenesis. Notably, some SARS-CoV accessory proteins have been shown to modulate the interferon signaling pathways and the production of pro-inflammatory cytokines. The structural information on these proteins is also limited, with only two (p7a and p9b) having their structures determined by X-ray crystallography. This review makes an attempt to summarize the published knowledge on SARS-CoV accessory proteins, with an emphasis on their involvement in virus–host interaction. The accessory proteins of other coronaviruses are also briefly discussed. This paper forms part of a series of invited articles in Antiviral Research on “From SARS to MERS: 10years of research on highly pathogenic human coronaviruses” (see Introduction by Hilgenfeld and Peiris (2013)).