A sequence-specific
ribozyme (M1GS
RNA) derived from the
catalytic RNA subunit of
RNase P from Escherichia coli was used to target the
mRNA encoding human cytomegalovirus (
HCMV) protease (PR), a
viral protein that is responsible for the processing of the viral capsid assembly
protein. We showed that the constructed
ribozyme cleaved the PR
mRNA sequence efficiently in vitro. Moreover, a reduction of about 80% in the expression level of the
protease and a reduction of about 100-fold in HCMV growth were observed in cells that expressed the
ribozyme stably. In contrast, a reduction of less than 10% in the expression of viral
protease and viral growth was observed in cells that either did not express the
ribozyme or produced a catalytically inactive
ribozyme mutant. Further examination of the
antiviral effects of the
ribozyme-mediated cleavage of PR
mRNA indicates that (1) the proteolytic cleavage of the capsid assembly
protein is inhibited significantly, and (2) the packaging of the viral genomic
DNA into the CMV capsids is blocked. These observations are consistent with the notion that the
protease functions to process the capsid assembly
protein and is essential for viral capsid assembly. Moreover, our results indicate that the
RNase P ribozyme-mediated cleavage specifically reduces the expression of the
protease, but not other viral genes examined. Thus, M1GS
ribozyme is highly effective in inhibiting HCMV growth by targeting the PR
mRNA and may represent a novel class of general gene-targeting agents for the studies and treatment of
infections caused by human viruses, including HCMV.