The importance of ribosomes is clear. They are obligatory for gene expression, and large numbers are required for even slow cell growth. That ribosomal RNA accounts for half of the transcripts in cells has facilitated studies of the formation and metabolism of large ribosomal precursors which contain up to 20% "extra" sequences that are processed away as they mature to produce rRNA and form ribosomes. The processing pathway itself has been made clear but three main features remain poorly understood. In this grant, Dr. Schlessinger will focus on these features: the mechanism of formation of mature rRNA termini in E. coli; the link, if any, between protein synthesis and rRNA processing; and the sequences in precursor rRNA required to induce for rRNA formation or processing and how they function. The enzymes and factors required to form the mature termini of 16s and 23s rRNA in vitro will be identified. The nature of the minimal substrate will also be assessed, as will the features of protein synthetic conditions required to optomize the processing reactions. Site specific mutagenesis will be applied to produce systematic deletions of "extra" spacer sequences at the ends of 16s mRNA. The resulting mutants will be studied in vivo. Additionally, the secondary structure of the rRNAs will be examined by electron microscopy. The investigator has long been a major contributor in this area and this proposal indicates that he will continue to be. Support with a very good priority is recommended.
