PROJECT SUMMARY MicroRNAs (miRNAs or miRs) are genome-derived, functional noncoding RNA (ncRNA) molecules that govern posttranscriptional regulation of target gene expression in cells. Our long-term objective is to gain a mechanistic understanding of miRNA-controlled regulation of xenobiotic & nutrient disposition and drug actions towards the development of new therapeutic strategies. My laboratory pioneered the research on miRNA pharmacoepigenetics that has offered new insights into inter-individual variability in drug disposition and response. Since the diseased carcinoma cells are addicted to continuous supply and metabolism of key xenobiotic nutrients (e.g., amino acids or AAs, vitamins, sugars, etc.) for uncontrolled proliferation and tumorigenesis, understanding the roles of metabolic enzymes (e.g., pyridoxine-5-prime-phosphate oxidase or PNPO) and transporters (e.g., AA transporter SLC7A5/LAT1, glucose transporter SLC2A1/GLUT1, etc.) in nutrient metabolism and transport may help to identify new therapeutic targets. Yet, there is a critical gap in the understanding of important regulatory factors and mechanisms underlying key nutrients’ disposition and homeostasis in carcinoma cells. In addition, current research on miRNA functions and therapeutics are limited to the use of chemo-engineered miRNA “mimics” made in vitro and comprised of extensive and various types of chemical modifications, which are completely different from natural RNA molecules produced and folded in living cells without any or just carrying a limited number of posttranscriptional modifications. This is also in sharp contrast to protein research and therapy that have found ultimate success by using recombinant or bioengineered proteins produced and folded in living cells, rather than polypeptides or proteins synthesized chemically in vitro. Very recently, we have established a novel tRNA/pre-miRNA-based RNA bioengineering technology that permits high-yield and large-scale production of recombinant miRNA agents through in vivo bacterial fermentation. Our studies have showed that recombinant miRNAs are biologically active in regulating target gene expression in human cells, and subsequently modulate drug disposition and response. Furthermore, our preliminary studies have revealed that particular human tRNA (htRNA) can be coupled with human pre-miRNA (hsa-pre-miR) as novel carriers for the production of fully-humanized recombinant or bioengineered miRNA agents, namely hBERA/miRNA. Therefore, in this application, we proposed to (1) establish and utilize novel ncRNA carriers to produce a collection of recombinant hBERA/miRNA molecules (Aim 1), (2) delineate the mechanistic actions of recombinant miRNAs in the control of cellular vitamin B6 metabolism and AA metabolome/homeostasis (Aim 2), and (3) define the effectiveness of recombinant miRNAs in the modulation of pharmacodynamics in disease animal models in vivo (Aim 3). The proposed research will establish a one-of-a-kind RNA...