Nucleocapsid Protein of SARS-associated Coronavirus Upregulates the Transcription of hfgl2 Prothrombina -se/fibroleukin Gene

The structural protein of SARS-associated coronavirus (SARS-CoV) responsible for the activation of hfgl2 gene was investigated. Gene fragments encoding the nucleocapsid, the membrane, and spike proteins were amplified by RT-PCR, and they were cloned into the eukaryotic expression vector pcDNA3.1（+）. The plasmids were verified by restriction endonuclease analysis and sequencing. Chinese hamster ovary (CHO) cells were co-transfected with a plasmid carrying the hfgl2 promoter/luciferase and with one of the recombinant plasmids containing the genes enconding the N, M and S structural proteins. Luciferase activity was assayed as a measure of promoter function. Immunohistochemistry showed that genes encoding the structural protein of SARS-CoV were successfully expressed only in those cells transfected with the recombinated plasmids. Co-transfection of N gene expression construct with the reporter construct containing hfgl2 promoter in CHO cells showed a remarkable increase in luciferase activity compared with nontransfected cells. However, there was no significant difference in luciferase activity in cells cotransfected with pcDNA3.1-M and with pcDNA3.1-S2 along with hfgl2 promoter/ luciferase reporter gene. We conclude that the nucleocapsid protein of SARS-CoV upregulates the transcription of hfgl2 prothrombinase/fibroleukin gene.