Ribozymes of the hepatitis delta virus: Recent findings on their structure, mechanism of catalysis and possible applications

Although the delta ribozymes have been studied for more than ten years the most important information concerning their structure and mechanism of cata lysis were only obtained very recently. The crystal structure of the genomi c delta ribozyme turns out to be an excellent example of the extraordinary properties of RNA molecules to fold into uniquely compact structures. Detai ls of the X-ray structure have greatly stimulated further studies on the fo lding of the ribozymes into functionally active molecules as well as on the mechanism of RNA catalysis. The ability of the delta ribozymes to carry ou t general acid-base catalysis by nucleotide side chains has been assumed in two proposed mechanisms of self-cleavage. Recently, considerable progress has been also made in characterizing the catalytic properties of trans-acti ng ribozyme variants that are potentially attractive tools in the strategy of directed RNA degradation.