Hepatitis Delta Virus Ribozyme

The hepatitis delta virus (HDV) ribozyme is a non-coding RNA that is necessary for viral replication and is thought to be the only catalytic RNA known to be required for viability of a human pathogen. The ribozyme acts to process the RNA transcripts to unit lengths in a self-cleavage reaction. The ribozyme is found to be active in vivo in the absence of any protein factors and is the fastest known naturally occurring self-cleaving RNA.

The crystal structure of this ribozyme has been solved using X-ray crystallography and shows five helical segments connected by a double pseudoknot.

In addition to the sense (genomic version), all HDV viruses also have an anti-genomic version of the HDV ribozyme. This version is not the exact complementary sequence but adopts the same structure as the sense (genomic) strand. The only "significant" differences between the two are a small bulge in P4 stem and a shorter J4/2 junction.

The hepatitis delta virus ribozyme is structurally and biochemically related to the Mammalian CPEB3 ribozyme. Unrelated sequences with high similarity to the HDV ribozyme have evolved through convergent evolution (e.g. in the R2 RNA element).