A RNA-trimming plasmid pRG523 is constructed, in which three Rz genes, GR5(5'-cis-Rz gene), HR2G(trans-Rz gene) and GR3(3'-cis-Rz gene), are arranged in the order from 5' to 3' downstream from the T7 promoter. In vitro transcription of this plasmid shows that the trans-Rz can be trimmed to definite lengths by the cis-Rz on both sides of the trans-Rz. In vitro cleavage of HPV16 E6 and E7 RNA fragments of different lengths by synthetic Rz and that of E7 RNA with a length of 171 nt by synthetic Rz and transcribed Rzs with different lengths of flanking sequences is studied. The results show that the non-base-pairing flanking sequences on both Rz and target RNA can affect the cleavage reaction.
