Molecular Advances in Severe Acute Respiratory Syndrome-associated Coronavirus (SARS-CoV)

Chow, Ken Yan Ching; Hon, Chung Chau; Hui, Raymond Kin Hi; Wong, Raymond Tsz Yeung; Yip, Chi Wai; Zeng, Fanya; Leung, Frederick Chi Ching

Soon after the identification of the SARS-CoV, laboratories started to investigate the phylogenetic relationship between the virus and the other members of the same family through extensive comparison of their genome sequences. In mid-April 2003, the British Columbia Cancer Agency (BCCA) Genome Science Center in Canada (12 ) , the Center of Disease Control in the United States (13 ) and the University of Hong Kong (14 ) announced at nearly the same time that the complete genome sequence of the SARS-CoV had been isolated in the corresponding areas (15 ) . The results of independent sequencing of the SARS-CoV genome all indicated that it was a polyadenylated genomic RNA of 29.7 Kb in length. Comparative analysis of the genome with other coronaviruses suggested that the virus genome was very similar to previously characterized coronaviruses, with the order (starting from the N-terminal): replicase (R), spike (S), envelope (E), membrane (M) and nucleocapsid (N) gene, where there are few accessory genes or motifs spanning between the structural genes and at the 3 UTR (untranslated region), which may not be necessary for viral replication (12 ) . The replicase gene, with two open reading frames (ORF) 1a and 1b, covering more than two thirds of the genome, is predicted to encode only two proteinases (12 -14 ) that regulate both the replication of the positive-stranded genomic RNA and the subsequent transcription of a nested set of eight subgenomic (sg) mRNAs (Table 1; ref. 16 ), which is a common transcription strategy adopted by coronavirus members (17 -21 ) .