Nilgun Tumer Professor Rutgers University Dept. of Plant Pathology Biotechnology Center for Agriculture and the Environment 208B Foran Hall School of Env & Biol Sciences 59 Dudley Road New Brunswick. NJ 08901-8520 (732) 932-8165. ext. 215 FAX - 6535 tumer@aesop.rutgers.edu

Viral replication and virus resistance in transgenic plants

Major focus of the research in our laboratory is studying the mechanism by which ribosome inactivating proteins (RIPs) inhibit cellular translation and viral infection. Pokeweed antiviral protein (PAP). a ribosome inactivating protein from Phytolacca americana inhibits translation by catalytically removing a specific adenine residue from the large rRNA of the 60S subunit of eukaryotic ribosomes. In addition to its ribosome inactivating ability. PAP has potent activity against many plant and animal viruses including HIV. PAP has been targeted to cancer cells as the cytotoxic moiety of immunotoxins and has shown significant clinical antileukemic activity. Our research involves understanding the mechanism of cytotoxicity and antiviral activity of PAP. We have demonstrated that expression of PAP in transgenic plants leads to broad spectrum virus resistance. We investigated the mechanism of cytotoxicity of PAP and demonstrated that cytotoxicity is not solely due to enzymatic activity. but appears to involve different domains of the protein. We expressed several non-toxic PAP mutants in transgenic plants and demonstrated that antiviral activity of PAP can be separated from its cytotoxicity. We recently showed that PAP inhibits frameshifting and retrotransposition of Ty1 in yeast and identified yeast chromosomal mutants that are resistant to PAP. Our current research focuses on characterizing these host genes and determining their role in ribosome depurination and virus resistance.

Selected Publications

Jetzt AE, Cheng JS, Tumer NE, Cohick WS. (2009) Ricin A-chain requires c-Jun N-terminal kinase to induce apoptosis in nontransformed epithelial cells. Int J Biochem Cell Biol. 41(12):2503-10.

Li XP, Chiou JC, Remacha M, Ballesta JP, Tumer NE. (2009) A two-step binding model proposed for the electrostatic interactions of ricin a chain with ribosomes. Biochemistry. 48(18):3853-63.

Chiou JC, Li XP, Remacha M, Ballesta JP, Tumer NE. (2008) The ribosomal stalk is required for ribosome binding, depurination of the rRNA and cytotoxicity of ricin A chain in Saccharomyces cerevisiae. Mol Microbiol. 70(6):1441-52.

Baldwin AE, Khan MA, Tumer NE, Goss DJ, Friedland DE. (2008) Characterization of pokeweed antiviral protein binding to mRNA cap analogs: Competition with nucleotides and enhancement by translation initiation factor iso4G. Biochim Biophys Acta. 1789(2):109-16.

Parikh BA, Tortora A, Li XP, Tumer NE. (2008) Ricin inhibits activation of the unfolded protein response by preventing splicing of the HAC1 mRNA. J Biol Chem. 283(10):6145-53.

Baykal U, Tumer NE. (2007) The C-terminus of pokeweed antiviral protein has distinct roles in transport to the cytosol, ribosome depurination and cytotoxicity. Plant J. 49(6):995-1007.

Li XP, Baricevic M, Saidasan H, Tumer NE. (2007) Ribosome depurination is not sufficient for ricin-mediated cell death in Saccharomyces cerevisiae. Infect Immun. 75(1):417-28.

Di R. Tumer NE. (2005) Expression of a truncated form of ribosomal protein L3 confers resistance to pokeweed antiviral protein and the Fusarium mycotoxin deoxynivalenol. Mol Plant Microbe Interact. 18(8):762-70.

Parikh BA. Baykal U. Di R. Tumer NE. (2005) Evidence for retro-translocation of pokeweed antiviral protein from endoplasmic reticulum into cytosol and separation of its activity on ribosomes from its activity on capped RNA. Biochemistry. 44(7):2478-90.

Hudak. K.. Parikh. B.. Rong. D.. Santana. M.. Baricevic. M.. Seskar. M. and Tumer. N. E. (2004). Generation of pokeweed antiviral protein mutations in Saccharomyces cerevisiae: Evidence that ribosome depurination is not sufficient for cytotoxicity. Submitted.

Popescu. S. and Tumer. N. E. (2004). Silencing of ribosomal protein L3 genes in N. tabacum reveals coordinate expression and significant alterations in plant growth. development and ribosome biogenesis. The Plant Journal:39:29-44.

Parikh. B. and Tumer. N. E. (2004). Antiviral activity of ribosome inactivating proteins in medicine. Mini-reviews in Medicinal Chemistry 4:529-549.

Di. R. . Kim. J.. Martin. M. N.. Leustek. T.. Jhoo. J.. Ho. C.-T. and Tumer. N. E. (2003). Enhancement of the primary flavor compound methional in potato by increasing the level of soluble methionine. J. Agricultural and Food Chemistry 51:5695-5702.

Vivanco. J. M. and Tumer. N. E. (2003). Translation inhibition of capped and uncapped viral RNAs mediated by ribosome-inactivating proteins. Phytopathology 93:588-595.