Physiological role of genes involved in taurine biosynthesis in fishes and in silico approach to determine transcription factors in their promoters’ zone

Taurine, an amino sulfonic acid that is sometimes referred to as an amino acid, is endogenously synthesized by the action of the key genes/enzymes: cysteine dioxygenase (cdo), cysteine sulfonate decarboxylase (csad), glutamate decarboxylase (gad), and 2-amino ethanethiol dioxygenase (ado). The taurine transporter (taut) also distributes this taurine formation across the plasma. These genes have been identified as important in different physiological processes such as reproduction, digestion, olfactory, visual, circulatory, and muscular systems. Thus, a literature review of these genes in fish has been described in the present work. Moreover, there is null information regarding the study of regulatory elements such as transcription factors (TFs) in taurine biosynthesis and transportation genes of fishes. In this interest and taking advantage of the availability of different sequence databases, bioinformatics can be applied as a first approach for an in silico identification of the putative TFs and transcription factor binding sites (TFBS) that might play an important role in regulating these genes. The results showed that some are commonly shared, whereas TFs and TFBs vary among fish species. Hence, binding sites for homeobox protein BarH-like 1 (BARX1), brain-specific homeobox protein homolog (BSX), helicase-like transcription factor (HLTF), homeobox protein Hox-A7 (HOXA7), homeobox protein Hox-B3 (HOXB3), homeobox protein Hox-B6 (HOXB6), homeobox protein Meis1 (MEIS1), homeobox protein Meis3 (MEIS3), nuclear factor of activated T cells 1 (NFATC1), and homeobox protein Nkx-6.2 (NKX6-2) were commonly found in the promoter regions of genes involved in taurine transportation and biosynthesis. Additionally, our results suggested that the frequency of HOXB3, a transcription factor involved in development, has repetitive TFBS sites in the promoter region of all species analyzed in the present study. Although bioinformatics gives us an approach to determine putative TFs and TFBS, further work is needed to verify how the found regulatory elements play a key role in taurine biosynthesis and transportation.