Two trans-acting hammerhead ribozymes (Rzs), Rz1-2 and Rz4-9, were designed and shown to be effective in cleaving rat or mouse metallothenein (MT)-I and MT-II mRNA, respectively, at position +147/148, in a sequence-specific manner. The catalytic efficiency for Rz1-2 on rat MT-I was found to be 678 M(-1)s(-1) and that for Rz4-9 on rat MT-II cRNA was found to be 372 M(-1)s(-1). An expression vector, pRz(4-9/1-2), containing both Rzs linked in tandem, was constructed and used to transfect NbE-1 cells, an immortalized ventral prostate epithelial cell line. Two stable-transfected lines, NbE-1(Rz2) and NbE-1(Rz3), expressing substantial levels of (Rz1-2/Rz4-9) and minimal levels of MT-I and MT-II transcripts were found to exhibit increased sensitivity to cadmium (Cd)-induced cytotoxicity compared to the parent line. This article is the first to report successful degradation of rodent MT mRNA in vitro and in cellulo by hammerhead Rzs.
Copyright 1999 Academic Press.