Cross-kingdom regulation of tRNAs/tRFs derived from Chinese yew

Abstract

Plants containing countless chemical constituent have benefited mankind since the origin of life. Although secondary metabolites in plants, such as morphine, artemisinin and taxol, have been developed as therapeutic drugs for clinical therapy, few study focuses on the pharmacological activities of plant small RNAs with function of cross-kingdom regulations. Yew is widely considered as a \"superstar\" plant due to the discovery of paclitaxel, or taxol, which is a well-known natural drug for the treatment of multiple types of cancer1. Here we show the surprising finding that an RNA fragment, named tRF-T11, derived from tRNAHis(GUG) of Chinese yew strongly suppressed human ovarian cancer progression. In A2780 cells, tRF-T11 mimic (a double-stranded RNA with tRF-T11 as antisense chain) exhibited potent cytotoxicity comparable to that of taxol, but no significant cytotoxicity to normal ovarian surface epithelial cells. Moreover, the cytotoxicity of tRF-T11 mimic is 80-fold stronger than that of taxol in taxol-resistant A2780 cells. Bioinformatic and molecular biological studies revealed that tRF-T11 targets transient receptor potential cation channel subfamily A member 1 (TRPA1) to inhibit its expression levels. In a further in vivo investigation, the growth rate of ovarian tumor xenografts in nude mice was significantly reduced by treatment with tRF-T11 mimic, and the TRPA1 protein expression in tumors treated with tRF-T11 mimic was also down-regulated. Our findings are the first to provide evidence that plant-derived tRFs can regulate the expression of target genes in vitro and in vivo, indicating that they may become as a new source of druggable siRNA. Moreover, this discovery demonstrated a pilot example of an innovative approach for not only identifying pharmacologically-active tRFs from plants, but also for improving the efficiency and possibilities of discovering new drug target.