John Woolford

Professor of Biological Sciences and Co-Director of CNAST

As the ubiquitous cellular factories that catalyze the synthesis of proteins, ribosomes are essential for and closely linked to regulation of growth, proliferation, and adaptation of cells. Consequently, investigations of developmental defects or the pathogenesis of many diseases related to alterations in cell growth or proliferation involve studies of ribosome biogenesis and function. The Woolford laboratory is investigating how ribosomes are assembled. We use the yeast Saccharomyces cerevisiae, to facilitate combined genetic, molecular biological, biochemical, and proteomic approaches. Ribosome assembly initiates in the nucleolus, where rRNA is transcribed, associates with ribosomal proteins, and undergoes modification and processing to form mature rRNAs. Subsequent steps in maturation of preribosomal particles occur upon their release from the nucleolus to the nucleoplasm and upon their export to the cytoplasm. Assembly of functional ribosomal subunits requires a dynamic series of remodeling steps wherein protein-protein, RNA-protein and RNA-RNA interactions are established, disrupted and reconfigured. Screens for yeast mutants defective in ribosome biogenesis, and development of methods to purify ribosome assembly intermediates and identify their constituents, led to the identification of >170 trans-acting factors required  for ribosome assembly. Central to understanding the mechanisms of ribosome biogenesis will be to figure out the precise roles played by each of these assembly factors. Which of them contacts pre-rRNA? Which proteins interact with each other? Can one define assembly neighborhoods within the nascent rRNPs, as observed for prokaryotic ribosomes assembled in vitro? In what order do these factors associate with preribosomes, carry out their functions, then dissociate from the particles? By what means are assembly factors and ribosomal proteins recruited to preribosomes, activated, then released from the pre-rRNPs? Experiments are underway to address these questions.

Lab Webpage: http://www.bio.cmu.edu/labs/woolford