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Environmental Factor, June 2012

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Upcoming distinguished lecturer Rachel Green

By Brant Hamel

Rachel Green, Ph.D.

Green is a synthesizer, both of the disciplines of chemistry and biology, and of the investigations of RNA translation and evolutionary biology. (Photo courtesy of Rachel Green)

The 2011-2012 NIEHS Distinguished Lecture Series will welcome Rachel Green, Ph.D., June 12 at 11:00 a.m. in Rodbell Auditorium, where she will give a talk titled “Quality Control on the Ribosome During Translation.” Green’s visit is hosted by Traci Hall, Ph.D., lead researcher and head of the Macromolecular Structure Group at NIEHS.

Green is a professor of molecular biology and genetics at Johns Hopkins University School of Medicine and a Howard Hughes Medical Institute Investigator (HHMI). She obtained her B.S. from the University of Michigan, a Ph.D. in biological chemistry from Harvard University, and completed her postdoc at the University of California, Santa Cruz. 

Author of more than 50 papers, many of them published in high impact journals, Green also serves on editorial boards for the journals RNA, the BMC Journal of Biology, and Molecular Cell. In addition to her HHMI honors, she has won numerous awards, including a Burroughs Wellcome Career Award, a Searle Scholarship Award, and a David and Lucille Packard Fellowship Award. Proving that her commitment to teaching is just as great as her dedication to research, Green was selected as the John Hopkins University School of Medicine Teacher of the Year in 2005. In May, the National Academy of Sciences announced the election of Green as a member, in recognition of her distinguished and continuing achievements in original research.

The Green lab focuses on understanding the mechanism of translation by the ribosome as well as its regulation by extra-ribosomal factors. Her research touches on the RNA world, a concept that the earliest life forms used RNA as both an informational template and as catalytic machinery, prior to the evolution of DNA and protein biochemistry. In fact, during her graduate studies Green was able to engineer an RNA molecule capable of self-replication.

During her postdoc, Green became fascinated with understanding how the ribosome exerts such exquisite control over the fidelity of protein synthesis. She employs mutational and enzymological techniques to understand the function and regulation of both prokaryotic and eukaryotic ribosomes.  Green’s work has important clinical relevance, as many antimicrobials target ribosomal function. Her distinguished lecture will focus on the myriad mechanisms ribosomes utilize to ensure the correct translation of RNA to protein.

Citation: Djuranovic S, Nahvi A, Green R. 2012. miRNA-mediated gene silencing by translational repression followed by mRNA deadenylation and decay. Science 336(6078):237-240.

(Brant Hamel, Ph.D., is an Intramural Research Training Award fellow in the NIEHS Molecular Endocrinology Group of the Laboratory of Signal Transduction.)

Quality control during translation in bacteria and yeast (abstract by Rachel Green, Ph.D.)

Accurate translation of the genetic information is a defining feature of the ribosome and the translation factors. Here we focus on quality control during translation in two different organisms, E. coli and S. cerevisiae. While much is known about the events that lead to ribosomal discrimination against the incorporation of the wrong amino acid (the process known as tRNA selection), less is known about the ribosomal response following a miscoding event. Using a well-defined in vitro bacterial translation system, we identified an unanticipated quality control system on the ribosome that monitors fidelity retrospectively. The in vitro and in vivo approaches that we have used to define this quality control system will be described. We have also begun to define the biochemical parameters of quality control systems in an in vitro reconstituted yeast translation system. In these studies, we have shown that two factors implicated in no-go decay, Dom34 and Hbs1, promote subunit dissociation and peptidyl-tRNA drop-off on the ribosome to initiate the recycling events that eventually lead to mRNA decay. Our most recent work has focused on understanding how the multifunctional ABC-family protein Rli1 contributes to translational termination and recycling. All of these results will be discussed with a view towards defining the relationship (i.e. coupling) between termination and recycling in bacteria and eukaryotes.

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