Molecular Cloning, Expression, and Anti-Cancer Activity of SBP1 Gene in Whitetip Reef Shark

SBP1 (selenium-binding protein 1) plays a key role in a variety of cancers. At present, most researches have focused on model organisms, while few studies have explored the SBP1 of unknown genome species. In the early stage of this study, based on the discovery of the high selenium content and the SBP1 peptide signal in the whitetip shark, the SBP1 cDNA sequence of the whitetip reef shark was first cloned and sequenced. The fulllength cDNA of the whitetip reef shark SBP1 gene is 3 064 bp and contains a 1 419 bp open reading frame that encodes 472 amino acids. There are 15 histidine residues within its protein sequence, accounting for 3.2%. It contains two CxxC, two HxD and three HxxH conserved regions. The three-dimensional structural model of SBP1 was constructed by SWISS-MODEL, and it was deduced that the 56th serine (Ser56) located at the junction between the β-sheet and structural loop was the selenium binding site. Phylogenetic tree analysis shows that whitetip shark and elephant shark have the highest SBP1 homology. After transfecting the recombinant MYC-SBP1 and the empty vector pcDNA3.1-MYC into HL-7702, HepG2 and HeLa cells respectively, Cell Counting Kit-8 and CFDA SE cell proliferation tracer fluorescent probe were used to investigate the anti-cancer function of shark SBP1. It was found that whether or not Na2SeO3 was added in medium, the expression of the recombinant protein SBP1 in HeLa and HepG2 cancer cells would significantly inhibit cell proliferation. In contrast, the SBP1 expression group promotes the proliferation of normal HL-7702 cells. This study speculates that the chemopreventive effect of selenium is highly related to the function of SBP1. To some extent, it may be SBP1 protein rather than selenium plays a more critical role in cancer prevention.

CSTR: 32200.14.cjcb.2022.05.0002