Molecular Cloning and Bioinformatics Analysis of APEX1, a DNA Base Excision Repair Enzyme from the Tianzhu White Yak（Bos grunniens）

The molecular genetics of searching candidate gene on high-attitude adaptability and resistance to cold has become a worldwide hot topic in plateau biology, especial in human and yak. APEX1 as a reference gene, playing a crucial role in Base Excision Repair (BER) enzyme, researches about yak APEX1 can help to understand the adaption of yak in plateau, and then further to increase its economic value. Full length cDNA sequence of apurinic/ apyrimidinicsite endonuclease 1 (APEX1) was cloned from Tianzhu white yak to study the roles of APEX1 and its mechanisms in stress resistance. PCR and RACE techniques were used to obtain the full length of APEX1 cDNA sequence. The result indicated that the full length cDNA of yak APEX1 was 1391 bp (GenBank accession No. KF611690), with an ORF 957 bp encoding 318 amino acids. The amino sequence analysis indicated that APEX1 was highly conserved in most mammals. The predicted molecular weight and pI of yak APEX1 were 35.1 KDa and 7.82, respectively. According to the analysis of APEX1 amino acid in Tianzhu white yak, APEX1 was a kind of hydrophilic, but not a secreted and transmembrane protein. The predicted 3D structure of APEX1 has similar folds and topology with that of human APEX1. The relative expressions of APEX1 in the liver, heart, testis, ovary, lung, brain, muscle, spleen and kidney were detected by quantitive real-time PCR, the result suggested that the highest expression level of yak APEX1 mRNA was in brain, and followed by ovary, spleen and kidney.