In general the largest mature derivative in the processing of precursor 45S ribosomal RNA (rRNA) is 26S-28S rRNA, a component of the large ribosomal subunit. Little is known about the structural elements, interacting molecules, and machinery needed to remove transcribed spacers from eukaryotic rRNA. In some eukaryotic Z6S-Z8S rRNA is further fragmented into alpha and beta halves, held together by hydrogen bonding. There is also a dearth of information about the phenomenon, which is called gap processing. The long term goals of the project are to determine the recognition signals and mechanisms involved in gap processing and to ascertain its role in ribosome function. The specific objectives of this proposal are to: 1) determine the interaction of ribosomal protein L25 with the gap region in the fungus fly Sciara coprophila by in vitro binding experiments; 2) determine the structure of rRNA in the gap region using strand-specific nucleases as probes and primer extension analysis; 3) localize the site of gap processing by subcellular fractionation of Tetrahymena; and 4) determine the fate of the excised rRNA by hybridization and S1 nuclease or Northern blot analyses. These studies should provide a better understanding of gap processing and the expression of mature rRNA in eukaroyotes.
