Functional Analysis of the Promoter Regions of Two Apoptosis-Related Genes ( and ) and Their Regulation by Zn in Yellow Catfish.

B-cell lymphoma 2 (Bcl-2) and cytochrome c (Cycs) are two important proteins relevant to cellular apoptosis. In this study, we characterized the functions of the promoter regions of two apoptosis-related genes, and , in yellow catfish . We obtained a 1989 bp promoter and an 1830 bp promoter and predicted several key transcription factor binding sites (TFBSs) on the promoters, such as Kruppel-like factor 4 (KLF4), signal transducer and activator of transcription factor 3 (STAT3), forkhead box O (FOXO), metal-responsive element (MRE) and hepatocyte nuclear factor 1α (HNF-1α). Zinc (Zn) increased the activities of the promoter but decreased the activities of the promoter. Metal-responsive transcription factor 1 (MTF-1) and HNF-1α directly bound with and promoters, and they positively regulated the activity of the promoter but negatively regulated the activity of the promoter. Zn promoted the binding ability of HNF-1α to the promoter but decreased its binding ability to the promoter. However, Zn had no significant effect on the binding capability of MTF-1 to the regions of and promoters. Zn upregulated the mRNA and total protein expression of Bcl-2 but downregulated the mRNA and total protein expression of Cycs. At the same time, Annexin V-FITC/PI staining showed that Zn significantly reduced the apoptosis of primary hepatocytes. For the first time, our study provides evidence for the MRE and HNF-1α response elements on the and promoters, offering new insight into the mechanism by which Zn affects apoptosis in vertebrates.