RNA toxins are a group of enzymes that mediate an organism’s response to stress, either by causing apoptosis, regulating growth rate, facilitating a change in development or by directly targeting pathogens. They are nucleases or glycosidases that damage RNA, thereby inhibiting gene expression at the translation level. RNA toxins are broadly categorized into four groups, based on their enzyme activity (cleavage of phosphodiester bond or base) and substrates (rRNA, tRNA, or mRNA). The goal of our research is to understand the regulation and develop the application of a glycosidase synthesized by the pokeweed plant, called pokeweed antiviral protein (PAP). Our research involves a combination of molecular biology and bioinformatics.
Two current research areas: 1) Regulation of the antiviral response in pokeweed. We have recently published that a small negative-strand RNA in pokeweed binds specifically and cleaves the mRNA of our antiviral protein, reducing its expression. The small RNA is regulated by jasmonic acid, which is a plant signaling molecule that controls the expression of several defense genes. This finding prompted us to sequence the transcriptome and small RNA populations of pokeweed in the presence of jasmonic acid. We found that the majority of its transcripts have not been identified in other sequenced plants; therefore, pokeweed represents a valuable resource of potential new genes that may be involved in helping the plant survive pathogen attack. 2) Potential application of the antiviral protein against HIV-1. By transfecting cell lines with a cDNA encoding the antiviral protein and HIV-1 proviral clone, we have shown that expression of the enzyme decreases viral RNA synthesis, alters its splicing, and reduces HIV-1 protein levels, resulting in substantial decline in virus production. These effects are largely due to depurination of the viral genome by the antiviral protein, which terminates its replication. Our recently published work suggests that the antiviral protein improves the natural defense response of cells against HIV-1. We are currently investigating how the antiviral protein specifically targets the virus without being toxic.
Krivdova G. and Hudak K.A. 2015. Pokeweed antiviral protein restores levels of cellular APOBEC3G during HIV-1 infection by depurinating Vif mRNA. Antiviral Research, 122:51-54. doi: 10.1016/j.antiviral.2015.08.007.
Klenov A., Neller K.C.M., Burns L.A., Krivdova G. and Hudak K.A. 2015. A small RNA targets pokeweed antiviral protein transcript. Physiolia Plantarum, doi: 10.1111/ppl.12393.
Zhabokritsky A., Mansouri S. and Hudak K.A. 2014. Pokeweed antiviral protein alters splicing of HIV-1 RNAs, resulting in reduced virus production. RNA 20:1238-1247.
Krivdova G., Neller K., Parikh B. and Hudak K.A. 2014. Antiviral and antifungal properties of RIPs. In: Ribosome inactivating proteins: biology and applications. D.A. Lappi and F. Stirpe eds., John Wiley & Sons Inc., Hoboken, NJ. ISBN-10: 1118125657.
Mansouri S., Kutky M. and Hudak K.A. 2012. Pokeweed antiviral protein increases HIV-1 particle infectivity by activating the cellular mitogen activated protein kinase pathway. PLoS One, 7(5):e36369.
Zhabokritsky A., Kutky M., Burns L.A., Karran R.A. and Hudak K.A. 2011. RNA toxins: mediators of stress adaptation and pathogen defense. Wiley Interdisciplinary Reviews RNA, 2: 890-903.
Karran R.A. and Hudak K.A. 2011. Depurination of Brome mosaic virus RNA3 inhibits its packaging into particles. Nucleic Acids Research, 39: 7209-7222.