An efficient RNA‐cleaving DNA enzyme can specifically target the 5′‐untranslated region of severe acute respiratory syndrome associated coronavirus (SARS‐CoV)

Abstract Background The worldwide epidemic of severe acute respiratory syndrome (SARS) in 2003 was caused by a novel coronavirus called SARS‐CoV. We report the use of DNAzyme (catalytic DNA) to target the 5′‐untranslated region (5′UTR) of a highly conserved fragment in the SARS genome as an approach to suppression of SARS‐CoV replication. A mono‐DNA enzyme (Dz‐104) possessing the 10–23 catalytic motif was synthesized and tested both in vitro and in cell culture. Materials and methods SARS‐CoV total RNA was isolated, extracted from the SARS‐CoV‐WHU strain and converted into cDNA. We designed a RNA‐cleaving 10–23 DNAzyme targeting at the loop region of the 5′UTR of SARS‐CoV. The designed DNAzyme, Dz‐104, and its mutant version, Dz‐104 (mut), as a control consist of 9 + 9 arm sequences with a 10–23 catalytic core. In vitro cleavage was performed using an in vitro transcribed 5′UTR RNA substrate. A vector containing a fused 5′UTR and enhanced green fluorescent protein (eGFP) was co‐transfected with the DNAzyme into E6 cells and the cells expressing eGFP were visualized with fluorescence microscopy and analyzed by fluorescence‐activated cell sorting (FACS). Results and conclusions Our results demonstrated that this DNAzyme could efficiently cleave the SARS‐CoV RNA substrate in vitro and inhibit the expression of the SARS‐CoV 5′UTR‐eGFP fusion RNA in mammalian cells. This work presents a model system to rapidly screen effective DNAzymes targeting SARS and provides a basis for potential therapeutic use of DNA enzymes to combat the SARS infection. Copyright © 2007 John Wiley & Sons, Ltd.