Characterization of the promoter region of the bovine 3 gene: roles of SREBF2 and PPARG.

As a member of the Iroquois homeobox gene family, the 3 gene plays an important role in regulating the growth, development and fat deposition of chordates. In the present study, we found, using real-time PCR, that the bovine 3 gene was highly expressed in lung, kidney, heart, subcutaneous fat and longissimus dorsi muscle. We cloned the full-length sequence of the bovine 3 gene promoter and constructed eight series of 5' deletion promoter plasmid luciferase reporter assays and then transfected them to 3T3-L1 and C2C12 cell lines to detect its core promoter regions. The results showed that the core promoter of bovine 3 was located within a -292/-42 bp region relative to the transcriptional start site. Furthermore, sequence analysis identified eight CpG islands in the promoter region. A chromatin immunoprecipitation assay in combination with site-directed mutation and siRNA interference demonstrated that SREBF2 and PPARG binding occurs in region -292/-42 and is essential in bovine 3 transcription. These results lay an important theoretical foundation for exploring the molecular regulation mechanism of the 3 gene in bovine fat deposition.