Pokeweed Antiviral Protein and Inhibition of Ribosomal Frameshifting

Rutgers University New Brunswick, New Brunswick NJ

Investigators

Abstract

Pokeweed antiviral protein (PAP), a 29-kDa antiviral protein isolated from pokeweed plants catalytically removes two adenines and a guanine from the large rRNA and inhibits translation. PAP depurinates the large rRNA by binding to ribosomal protein L3. The investigators recently demonstrated that expression of PAP in yeast led to specific inhibition of +1 programmed ribosomal frameshifting (PRF) and interfered with the ability of the yeast retrovirus Ty1 to retrotranspose. Using nontoxic PAP mutants, they showed that PAP inhibited +1 PRF and Ty1 retrotransposition without inhibiting general translation. PAP had no effect on -1 PRF or maintenance of the yeast killer virus. These results suggested that PAP could be used as a specific probe to dissect the mechanisms regulating +1 PRF and as a general tool to study the role of translational fidelity in virus maintenance. The primary objective of this project is to use recombinant PAP mutants and yeast chromosomal mutants to investigate the mechanism by which PAP inhibits +1 frameshifting and Ty1 retrotransposition in yeast. PAP sequences critical for inhibition of +1 PRF and Ty1 retrotransposition, and PAP binding sites on ribosomal protein L3 will be identified. It will be determined whether binding of PAP to the ribosomes, to the large rRNA, and/or to L3 is critical for inhibition of +1 PRF. These studies provide a unique way to address questions relating to ribosome structure and function and may have important implications for understanding the unusual mechanism of translation inhibition by ribosome inactivating proteins. Alterations in PRF efficiencies can have profound effects on propagation of many important plant and animal viruses. Information gained from these studies could be used to design viral or cell specific translation inhibitors and may lead to development of more effective means of disease control in agriculture and medicine.