Structural analysis and core promoter prediction of STAR gene and its regulatory mechanism of progesterone synthesis in bovine luteal cells

The steroidogenic acute regulatory protein (STAR) plays a crucial role in facilitating cholesterol transfer across the inner mitochondrial membrane during the process of steroidogenesis. However, the transcriptional regulation of the bovine STAR gene and its function of progesterone synthesis in luteal cells remain poorly understood. The objective of this study was to analyze the bovine STAR gene structure, identify its active promoter region, and explore its potential roles in progesterone synthesis. Bioinformatics analysis revealed that the bovine STAR gene encodes an 858-bp mRNA transcript, which translates into a protein consisting of 285 amino acids. The phylogenetic tree analysis showed that its genetic distance was closest to that of sheep. Notably, the promoter region of bovine STAR lacks CpG islands, and the core promoter is located within the - 1990/-1 region, which containes potential binding sites for transcription factors such as NF-κB, Sp1, NF-1, and LyF-1. Dual-luciferase reporter assays confirmed the core promoter activity within this region, aligning with the prediction results. Overexpression of the STAR gene in bovine luteal cells significantly enhanced progesterone production and upregulated the expression of steroidogenic enzymes, particularly 3βHSD and CYP11A1. In conclusion, this study identifies the core promoter region of the bovine STAR gene is positioned at -1990/-1. By regulating key steroidogenic enzymes, particularly 3βHSD and CYP11A1, STAR is involved in the synthesis of progesterone in corpus luteum cells.