AN RIBOSOMAL-RNA FRAGMENT AND ITS ANTISENSE CAN ALTER DECODING OF GENETIC INFORMATION

rRNA plays a central role in protein synthesis and is intimately invol ved in the initiation, elongation, and termination stages of translati on. However, the mode of its participation in these reactions, particu larly as to the decoding of genetic information, remains elusive. In t his paper, we describe a new approach that allowed us to identify an r RNA segment whose function is likely to be related to translation term ination. By screening an expression library of random rRNA fragments, we identified a fragment of the Escherichia coli 23S rRNA (nucleotides 74 to 136) whose expression caused readthrough of UGA nonsense mutati ons in certain codon contexts in vivo. The antisense RNA fragment prod uced a similar effect, but in neither case was readthrough of UAA or U AG observed. Since termination at UGA in E. coli specifically requires release factor 2 (RM), oar data suggest that the fragments interfere with RF2-dependent termination.