The ribosome is the two-subunit macromolecular complex responsible for the translation of the genetic code into functional polypeptides. The ribosome is composed of RNA (3 large rRNAs in bacteria) and protein (more than 50 r-proteins in bacteria) in a mass ratio of about 2 to 1. We are interested in understanding how this ribonucleoprotein machine catalyzes and coordinates the complex molecular events of translation. These studies may reveal important details that impact on the function of other RNP machines such as the spliceosome and telomerase and may uncover clues that address the early origins of life and the potential of an ‘RNA world’. As ribosomes are the target of many clinically relevant anti-microbial agents (erythromycin, chloramphenicol, and the aminoglycosides), the implications of these studies for drug development are significant.

The work in our laboratory focuses on a number of different steps in the translational elongation and termination cycles. Recent advances in X-ray crystallography have provided us with atomic resolution views of the large and small subunits of the ribosome. The active sites of the large and small ribosomal subunits where tRNAs and release factors bind and interact are composed primarily of RNA. We have developed methodology to incorporate site-specific nucleotide changes in the catalytic core of the large and small subunits and to purify these mutant ribosomes for enzymological studies. Using rapid quench kinetic techniques and well-defined molecular systems, we are looking at the contributions made by specific nucleotides in the ribosome as well as the translation factors themselves to decipher the molecular mechanisms utilized by the protein synthesis machinery. Our recent studies have led to the identification of a number of specific molecular switches critical to multiple steps during elongation and termination. We are excited by the possibility that these inherent switches in the ribosome are in turn manipulated by extra-ribosomal factors to mediate certain forms of translational control. We are currently developing the tools to ask such questions in both purified bacterial and eukaryotic translation systems.

Publications:

Youngman, E.M., Brunelle, J.L., Kochaniak, A.B., Green, R. The active site of the ribosome is composed of two layers of conserved nucleotides with distinct roles in peptide bond formation and peptide release. Cell. 2004; 117: 589-99.
PubMed

Merryman, C., Green, R. Transformation of aminoacyl tRNAs for the in vitro selection of “drug-like” molecules. Chemistry & Biology. 2004; 11: 575-82.
PubMed

Cochella, L., Green, R. An active role for tRNA in decoding beyond codon:anticodon pairing. Science. 2005; 308: 1178-80.
PubMed

Dorner, S., Lum, L., Kim, M., Paro, R., Beachy, PA, Green, R. A genomewide screen for components of the RNAi pathway in Drosophila cultured cells. Proc Natl Acad Sci USA. 2006; 32: 11880-5.
PubMed

Cochella, L., Brunelle, J., Green, R. Mutational analysis reveals two independent molecular requirements during transfer RNA selection on the ribosome. Nat Struct Mol Biol. 2007;14:30-6.
PubMed