MESSENGER ACTIVITY OF NASCENT RIBOSOMAL RNA

Escherichia coli nascent rRNA containing little contamination of messenger RNA and mature RNA was prepared from chloramphenicol-particles or relaxed-particles. Cell-free amino acid-incorporation experiments using the purified nascent rRNA preparations showed that the messenger activities of 17 and 23 s nascent rRNA were six and three times those of 16 and 23 s mature rRNA, respectively. Protein synthesis directed by the nascent rRNA took place on 70 s ribosomes with which a part of the added nascent rRNA combined. Analyses by polyacrylamide gel electrophoresis of the products formed during cell-free protein synthesis in the presence of nascent rRNA showed that the bulk of those products had mobilities similar to those of ribosomal proteins and distinct to those of the products of messenger RNA-directed synthesis. It was concluded from these facts that nascent rRNA acts as a template for some polypeptide synthesis in vitro. © 1968.