A small nucleolar RNA : ribozyme hybrid cleaves a nucleolar RNA target in vivo with near-perfect efficiency

A hammerhead ribozyme has been localized to the yeast nucleolus by using th e U3 small nucleolar RNA as a carrier. The hybrid small nucleolar RNA:riboz yme, designated a "snorbozyme," is metabolically stable and cleaves a targe t U3 RNA with nearly 100% efficiency in vivo. This is the most efficient in vivo cleavage reported for a trans-acting ribozyme. A key advantage of the model substrate featured is that a stable, trimmed cleavage product accumu lates. This property allows accurate kinetic measurements of authentic clea vage in vivo. The system offers new avenues for developing effective ribozy mes for research and therapeutic applications.