ANALYSIS OF THE RIBOSOME LARGE SUBUNIT ASSEMBLY AND 23-S RIBOSOMAL-RNA STABILITY IN-VIVO

The ability of mutant 23 S ribosomal RNA to form particles with protei ns of the large ribosomal subunit in vivo was studied. A series of ove rlapping deletions covering the entire 23 S rRNA, were constructed in the plasmid copy of an E. coli 23 S rRNA gene. The mutant genes were e xpressed in vivo using an inducible tac promoter. Mutant species of 23 S rRNA, containing deletions between positions 40 and 2773, were inco rporated into stable ribonucleoprotein particles. In contrast, if one end of the 23 S rRNA was deleted, the mutant rRNA was unstable and did not form ribosomal particles. Protein composition of the mutant parti cles was specific; the presence of the primary rRNA-binding proteins c orresponded to their known binding sites. Furthermore, several previou sly unknown ribosomal protein binding sites in 23 S rRNA were identifi ed. Implications of the results on ribosome assembly are discussed. (C ) 1996 Academic Press Limited