LEAD-ION-INDUCED CLEAVAGE OF RNASE P RNA

Pb2+-induced hydrolysis of RNase P RNAs from Escherichia coli and the thermophilic eubacterium Thermus thermophilus HB8 revealed one promine nt site-specific cleavage in the two RNAs and several minor cleavage s ites in structurally corresponding regions of both RNAs. Data presente d here and in a previous study [Kazakov, S. & Altman, S. (1998) Proc. Natl Acad. Sci. USA 88, 9193-9197] provide evidence for several ubiqui tous metal-ion-binding sites in eubacterial RNase P RNA subunits. With the T. thermophilus RNase P RNA, susceptibility to Pb2+-induced stran d scission at the most prominent site was hypersensitive at the temper ature of highest enzyme activity (55 degrees C). Pb2+ hydrolysis at th is site was strongly reduced at a temperature of 37 degrees C, where p rocessing is also inefficient. For E. coli RNase P RNA, specific chang es in the lead hydrolysis pattern were observed due to the presence of excess tRNA. Thus, Pb2+-induced hydrolysis seems suitable to sense di fferent conformations of RNase P RNAs. The T. thermophilus RNase P RNA , in particular, displayed significant processing activity after sever e fragmentation by Pb2+, and therefore appears to be suited for recons tituting an active enzyme from RNA subfragments.