Identifying Physiological Factors and Genes Involved in Saccharomyces Cerevisiae Susceptibility to Ricin-induced Apoptosis

Jennifer Gallagher, Ph.D., Daniel Judge, Leon Wilson*
Department of Biology, West Virginia University, Morgantown, WV 26506

Presentation Category: Biological Sciences (Poster presentation)

Student’s Major: Biochemistry

Ricin-mediated cell death is not well described. Ricin depurinates the ribosomal active site and reduces translation in all eukaryotic cells. How the ricin-damaged ribosomes are detected is unknown. Reduction of protein synthesis via ricin leads to apoptosis but other chemicals that inhibit protein synthesis do not. An unexpected reduction in the Unfolded Protein Response (UPR) occurs when cells are exposed to ricin. Reduction in the UPR from ricin could occur because ricin may have another target other than the ribosomal active site. Yeast expressing a version of ricin that cannot exit cells will be used to determine UPR by measuring splicing of HAC1 that changes in response to UPR. DTT, which reduces disulfide bonds and changes how proteins are folded, will be used as a control. Ricin-damaged ribosomes stop translation, and stall. An active ribosome that is loaded on the message later will crash into the stalled ribosome leading to a disome. This structure may be what induces apoptosis because damage could prevent disassembly of the stalled ribosome. Hel2 is a protein that ubiquitinates stalled ribosomes that occur normally so that ribosomal subunits can be recycled. These translation initiation factors bind the same location on the ribosome that ricin damages. I will determine if Hel2 can recognize ricin-damaged ribosomes by measuring the growth of yeast cells overexpressing Hel2 while simultaneously expressing ricin and compare them to wildtype yeast. Overall, it is expected that ricin will cause the UPR to be suppressed. While Hel2 overexpression will help cells survive ricin poisoning.

Funding: Not funded

Program/mechanism supporting research/creative efforts: WVU's Research Apprenticeship Program (RAP) & accompanying HONR 297-level coursem