Research Interest:

Ribosome Function and Structure

Two complex ribonucleoptrotein particles, spliceosomes and ribosomes, play significant roles in the expression of the information of the DNA gene in the form of a functioning protein. Spliceosomes are composed of a few small nuclear ribonucleoproteins (snRNPs) plus spliceosome associated proteins; they catalyze the removal of non-coding intron sequences from the pre-messenger RNA. We have purified one form of this dynamic family of particles, the A-complex, and characterized it both biochemically and by electron microscopy. We have also begun (through electron microscopy) to map individual spliceosome components and are initiating experiments that will allow us to trace the course of the pre-mRNA as it traverses the spliceosome. Ribosomes, the sewing machines upon which all proteins are assembled, are made up of a few RNA molecules and several specific proteins, organized in two dissimilar subparticles that have both independent and shared functions. We use biochemistry to identify important ribosomal components and electron microscopy to localize them on the organelle. RNA segments are probed with complementary oligonucleotides that interfere in specific functions; antibodies to part of the probe or other visual markers allow it to be located in electron micrographs of the ribosome. Ribosomal proteins are studied using monoclonal antibodies to a single protein or with anti-hapten antibodies that react with a single chemically-modified protein that has been incorporated in vitro in a reconstituted ribosomal subunit. Our goal is the production of superimposed physical and functional maps of the spliceosome and each subunit of the ribosome.
Unrelated work deals with the biology of human ribonucleases. We study three related but differentiable ribonucleases, a pancreatic-type and a liver-type Rnase that are responsible for the bulk of the nucleolytic activity found in most tissues, and angiogenin, an nuclease that induces vascularization of solid tissues including tumors. A fourth protein, RNASIN, is an inhibitor of these three nucleases. We have characterized these enzymes, studied their distribution in normal and diseased tissues, and helped link liver-type ribonuclease to tryptophan-induced eosinophilia-myalgia syndrome. Current efforts are aimed at the determination of the site of synthesis and the intracellular localization each of these proteins.