Molecular characterization and expression patterns of adenosine deaminases acting on tRNAs in Dabry's sturgeon (Acipenser dabryanus)

Adenosine deaminases acting on tRNAs (ADATs) are involved in the formation of inosine in tRNAs, and they are members of the adenosine deaminase acting on RNA (ADAR) family of RNA editing enzymes. In this study, we analyzed and characterized two ADAT genes, AdADAT2 and AdADAT3, from Dabry's sturgeon (Acipenser dabryanus). The full-length cDNAs of AdADAT2 and AdADAT3 were 1704 and 1402 bp, respectively, and they encoded putative proteins of 188 amino acids and 355 amino acids, respectively. AdADAT2 and AdADAT3 genes contain six exons and two exons, respectively. The deduced amino acid sequences exhibit signature features of three residues (generally, one histidine and two cysteines) embedded in three characteristic motifs (motif I, II, and III). AdADAT2 and AdADAT3 mRNAs were expressed ubiquitously in the tissues of healthy A. dabryanus, with elevated levels in the intestine, middle kidney, head kidney, and spleen. In response to polyinosine-polycytidylic acid (poly I:C), the AdADAT2 mRNA level was significantly upregulated at 6 h post-stimulation (hps), but the AdADAT3 mRNA level was prominently downregulated at 6 hps. The different responses of the two genes to poly I:C indicate that they have different defense mechanisms against viruses.