Two HDV Ribozymes

The ribozymes from the genomic and antigenomic strand of HDV RNA are similar in sequence, but are not identical. This sequence similarity reflects, in part, the fact that the HDV RNAs (both genomic and antigenomic) are about 70% self-complementary such that each single-stranded circle could form a partial-duplex rod-like structure (Wang et al. 1986). Each ribozyme sequence is transcribed from a region of the respective template that is partially complementary to the other ribozyme. Not surprisingly then, both ribozymes catalyze the same reaction to cleave the RNA backbone, and both appear to use a similar mechanism of catalysis. Although small differences in the activity of the two ribozymes are detectable under some conditions, at this point those differences appear to be idiosyncratic and relatively minor (Wadkins and Been 1997; Wadkins et al. 1999, 2001). It remains possible that there are less subtle and biologically important differences in the two ribozymes; however, for the major points addressed in this review, the two ribozymes appear to behave identically.

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