SEQUENCE-SPECIFIC CLEAVAGE OF RNA BY A HYBRID RIBONUCLEASE-H

Site-specific cleavage of the 22-, 132- and 534-base RNAs by the DNA/p rotein hybrid RNase H were examined. The 22-base RNA was chemically sy nthesized, and 132- and 534-base RNAs were prepared by run-off transcr iption. The hybrid enzyme cleaves these RNAs, which contain a single t arget sequence, primarily at the unique phosphodiester bond within the target sequence. The hybrid enzyme performs multiple turnovers, and a l a substrate/enzyme ratio of 10:1 the RNAs are almost completely clea ved by the hybrid enzyme at 37 degrees C within 1 h. We propose that h ybrid RNase H molecules with various oligodeoxyribonucleotides functio n as RNA restriction enzymes and are useful for structural and functio nal studies of RNA.