SELF-CLEAVAGE ACTIVITY OF THE GENOMIC HDV RIBOZYME IN THE PRESENCE OFVARIOUS DIVALENT METAL-IONS

To identify the divalent metal ions that can support the self-cleavage activity of the genomic ribozyme of human hepatitis delta virus (HDV) , we tested the activity of various divalent metal ions in the ribozym e reactions catalyzed by HDV88 (683-770 nt) and 88DI3 (HDV88 with the sequence from 740 - 752 nt deleted). Among various metal ions tested, Mg2+, Mn2+, Ca2+ and Sr2+ efficiently supported the self-cleavage reac tions of the HDV88 and 88DI3 ribozymes. In the case of the 88DI3 riboz yme, other divalent metal ions, such as Cd2+, Ba2+, Co2+, Pb2+ and Zn2 +, were also able to support the self-cleavage reaction to some extent (< 10%). In the presence of spermidine (0.5 mM), the cleavage reactio n was promoted at lower concentrations of effective divalent metal ion s. The HDV ribozyme represents the only example of ribozyme to date of a ribozyme that catalyzes the self-cleavage reaction in the presence of Ca2+ ions as efficiently as it does in the presence of Mg2+ ions.