Fig. 2.

A reporter system to measure single-round versus multiple-round translation. (A) DNA encoding the hammerhead ribozyme was inserted into lacZ. Due to rapid cotranscriptional folding and cleavage of the ribozyme, only the lead (coupled) ribosome should be able to translate the entire mRNA, providing a measure of single-round translation (left pathway). An analogous reporter with an inactive hammerhead provides a measure of multiple-round translation (right pathway). (B) Sequence of the inserted hammerhead ribozyme between codons 581 and 582 of lacZ mRNA. The catalytic core of the ribozyme is boxed, with critical nucleotides indicated in bold. Mutated bases are labeled in red.