Modulation of HPV16 E7 translation by tRNAs in eukaryotic cell-free translation systems

Translational regulation of HPV16 E7 mRNA is of particular interest since the viral E7 protein has oncogenic activity. Here we report that additional supplementation of cell-free reticulocyte/wheat-germ translation systems with rat liver tRNA pool favors the expression of the viral oncoprotein E7 which otherwise is scarcely translatable. The translational activation is explained by the positive correlation between the frequency of the glutamic and aspartic codons in E7 mRNA, and the increased concentration of the corresponding tRNAs following tRNA supplementation. The present in vitro data suggest a link between E7 expression and cell conditions conductive to tRNA changes such as development, cell proliferation and aging.