Recoding RNA editing of antizyme inhibitor 1 predisposes to hepatocellular carcinoma

Better understanding of human hepatocellular carcinoma (HCC) pathogenesis at the molecular level will facilitate the discovery of tumor initiating events. Herein, transcriptome sequencing revealed that adenosine (A)-to-inosine (I) RNA editing of antizyme inhibitor 1 ( AZIN1 ) displays a high modification rate in HCC specimens. A-to-I editing of AZIN1 transcripts is specifically regulated by a denosine deaminase acting on RNA-1 (ADAR1) . The serine (S) → glycine (G) substitution at residue 367, located in β-strand 15 (β15), predicted a conformational change, induced a cytoplasmic-to-nuclear translocation, and conferred “gain-of-function” phenotypes manifested by augmented tumor initiating potential and more aggressive behavior. Compared with wild-type AZIN1 protein, the edited form possesses stronger affinity to antizyme, and the resultant higher protein stability promotes cell proliferation via the neutralization of antizyme-mediated degradation of ornithine decarboxylase (ODC) and cyclin D1 (CCND1). Collectively, A-to-I RNA editing of AZIN1 may be a potential driver in the pathogenesis of human cancers, particularly HCC.