Small interfering RNA inhibits SARS‐CoV nucleocapsid gene expression in cultured cells and mouse muscles

SARS‐CoV is a newly identified coronavirus that causes severe acute respiratory syndrome (SARS). Currently, there is no effective method available for prophylaxis and treatment of SARS‐CoV infections. In the present study, the influence of small interfering RNA (siRNA) on SARS‐CoV nucleocapsid (N) protein expression was detected in cultured cells and mouse muscles. Four siRNA expression cassettes driven by mouse U6 promoter targeting SARS‐CoV N gene were prepared, and their inhibitory effects on expression of N and enhanced green fluorescence protein (EGFP) fusion protein were observed. A candidate siRNA was proved to down‐regulate N and EGFP expression actively in a sequence‐specific manner. The expression vector of this siRNA was constructed and confirmed to reduce N and EGFP expression efficiently in both cultured cells and adult mouse muscles. Our findings suggest that the siRNA should provide the basis for prophylaxis and therapy of SARS‐CoV infection in human.