My laboratory is analyzing the biochemical and molecular mechanism of the processing of precursor ribosomal RNA as an example of the regulation of gene expression in eukaryotic cells. Ribosomal RNA is initially made in mouse cells as a large 14,000 nucleotide precursor which is subsequently cleaved at specific locations to generate the mature 18S, 28S, and 5.8S rRNA components of the functional ribosome. Very little is known about the mechanism of this processing and its regulation. We have developed an in vitro cell-free processing system from mouse tissue culture cells and are using the techniques of molecular biology to study the following questions: