Mimicry of the hepatitis delta virus replication cycle mediated by synthetic circular oligodeoxynucleotides

Background: Hepatitis delta virus (HDV) is a circular single-stranded RNA p athogen whose monomeric form results from self-processing. Although studies have examined minimal HDV ribozyme activities, the mechanism for forming t he circular virus remains unclear, and the trans catalytic properties of se lf-processed forms of HDV ribozymes have not been studied. In addition, HDV ribozymes have not previously been engineered to cleave a non-HDV sequence . Results: Long repeating RNAs have been produced from in vitro rolling-circl e transcription of synthetic circular oligodeoxynucleotides encoding cataly tically active Subsets of the entire antigenomic RNA virus. Like full-lengt h HDV, these multimeric RNAs undergo self-processing to monomer length; imp ortantly, cyclization is found to occur efficiently, but only in the presen ce of the circular template, Linear and circular monomer ribozymes and engi neered variants are shown to be active in cleaving HDV and HIV RNA targets in trans, despite having self-binding domains. Conclusions: Mimicry of the rolling-circle replication pathway for HDV repl ication has led to a new proposal for cyclization of HDV RNA. Under these c onditions, cyclization is mediated by the complementary circular template. In addition, it-has been shown that self-processed HDV ribozymes can be cat alytically active in trans despite the presence of antisense sequences buil t into their structure.