Princeton ACS Meeting and Graduate Student Awards Seminar, Monday, September 18, 2017
Frick Laboratory, Princeton University. Mixer 5:30 pm; Presentation 6:30 pm followed by dinner. Our speakers will be:
Dainan Mao, Princeton University – “Discovery of a Master Switch to Turn on Bacterial Secondary Metabolism”
Abstract: Bacteria produce numerous secondary metabolites that have been invaluable as therapeutics in a clinical setting or as molecular probes in research. These metabolites are synthesized by dedicated biosynthetic gene clusters (BGCs), which assemble architecturally complex molecules from simple precursors. The majority of BGCs in a given bacterium are not expressed under normal growth conditions and our understanding of how the expression of these gene clusters is silenced is in its infancy. I will describe how we have addressed this question in the model Gram-negative bacterium, Burkholderia thailandensis E264, using genetic, transcriptomic, metabolomic, and chemical approaches. We have found that a previously unknown LysR-type transcriptional regulator, which we name ScmR (secondary metabolite regulator), serves as a global gate-keeper of secondary metabolism in the stationary phase. . Deletion of this regulator (scmR) results in a hyperactive secondary metabolite producer both in vitro and in a worm model in vivo. Numerous known metabolites, including the silent virulence factor malleilactone, are found to be overproduced 18-200-fold. We also found new analogs of known molecules and cryptic metabolites that are produced in the scmR strain. Morphologically, the mutant shows a corrugated colony phenotype, compared to the smooth appearance of wt cells. Collectively, our data suggest that ScmR is a QS-regulated global regulator of secondary metabolism, morphogenesis, and virulence. A model for how quorum sensing and scmR coordinately silence production of secondary metabolites is proposed.
Biography: Dainan Mao is a graduate student in the lab of Professor Seyedsayamdost in the Department of Chemistry at Princeton University. She received her B. S. in biology in 2012 from University of Science and Technology of China, where she first worked on bacterial and yeast genetics. Her current research focuses on the activation and discovery of cryptic secondary metabolites from bacterial sources. She is interested in developing new approaches to activate bacterial cryptic biosynthetic gene clusters, and understanding the molecular mechanisms of activation. During her graduate study, she discovered a master regulator of bacterial secondary metabolism. Currently she is also working on a project that examines the molecular basis of pleiotropic elicitors of secondary metabolism.
Adam Stevens, Princeton University, “Design & Deployment of Enhanced Split Inteins”
Abstract: Protein splicing is a post-translational autoprocessing event in which an intervening protein (intein) spontaneously cleaves itself from a precursor protein while simultaneously ligating the adjacent residues (exteins) to form a native peptide bond. Due to the efficiency of this ligation reaction, inteins have found widespread use as tools in protein engineering and chemical biology. Naturally split inteins, which are separately expressed and then undergo association and splicing in trans, are of particular interest. However, applications of split inteins have been limited by a number of shortcomings, including issues of expression yield among protein-intein fusions and decreased splicing rates under certain extein contexts (extein dependency). Through a structural and mechanistic-guided approach, we have engineered split inteins with improved robustness and extein promiscuity. These enhanced split inteins were then applied to a number of protein engineering methods, such as the generation of head to tail cyclized proteins, the modification of a monoclonal antibody with a small molecule cargo, and the semisynthesis of cellular chromatin in isolated nuclei. Overall, we expect these engineered proteins to encourage the further use and development of protein trans-splicing in protein semisynthesis..
Biography: Adam was born and raised in New York City and earned a degree in chemistry from Johns Hopkins University in 2012. As an undergraduate, when he wasn’t occupied as a member of the university’s wrestling team, he studied the inhibitory effect of DNA lesions on base excision repair enzymes under the guidance of Dr. Marc M. Greenberg. He is currently a graduate student in the department of chemistry at Princeton University in the lab of Dr. Tom W. Muir. His graduate research was supported by a National Science Foundation Graduate Research Fellowship and has focused on studying the mechanistic details of protein splicing in order to design intervening proteins (inteins) with enhanced activity and stability. He expects to complete his graduate work at the end of 2017 and will shortly thereafter begin a postdoctoral fellowship with Dr. Wendell Lim at the University of California San Francisco.
Reservations: The meeting will be held in Frick Laboratory, Princeton University. The social mixer will begin at 5:30 pm in the CaFe area of Taylor Commons. The lecture will be held in the Auditorium at 6:30 pm followed by dinner in Taylor Commons (CaFe area). Frick Laboratory is located at the east end of the pedestrian bridge on Washington Rd, adjacent to the Weaver Track and Field Stadium. Parking is available in Lot 21, corner of Faculty Road and Fitzrandolph Road or other lots along Ivy Lane (see http://m.princeton.edu/map/).The seminar is free and open to the public. Reservations are required for dinner, which is $20 ($10 for students). Please contact Louise Lawter at firstname.lastname@example.org or 215-428-1475 by September 12 to make reservations. Reservations must be canceled no later than September 17 to avoid being billed for the dinner.