Three alternative promoters govern PGC-1α expression in chicken and are directly repressed by PPARγ

Peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) is a key transcriptional coactivator that orchestrates diverse physiological and pathological processes by interacting with factors such as PPARγ, PPARα, and NRFs. While extensively characterized in mammals, PGC-1α gene structure and regulation remain unexplored in chickens. Here, using 5' rapid amplification of cDNA ends (5' RACE), we identified three distinct first exons in chicken PGC-1α gene, indicative of three alternative promoters (P1, P2, and P3). Dual-luciferase reporter assays confirmed that all three alternative promoter regions displayed robust activity, exhibiting approximately 27.8-, 3.9-, and 6.0-fold higher reporter activity compared to the promoterless pGL3-Basic control vector, respectively. Bioinformatics analysis identified PPAR response elements (PPREs) in each promoter. Functionally, overexpression of either PPARγ1 or PPARγ2 inhibited luciferase activity from all three promoters and reduced endogenous expression of the corresponding transcript isoforms (cPGC-1α1, cPGC-1α2, and cPGC-1α3). Conversely, PPARγ knockdown enhanced the expression of all three isoforms in ICP2 cells. Chromatin immunoprecipitation (ChIP) assays confirmed PPARγ binding to all three promoter regions in vivo in chicken abdominal adipose tissue. Tissue expression profiling revealed distinct expression patterns for cPGC-1α isoforms. Importantly, an inverse correlation was observed between the expression levels of these isoforms and PPARγ in the adipose tissue of Northeast Agricultural University broiler lines divergently selected for abdominal fat content (NEAUHLF). Collectively, our findings establish that chicken PGC-1α transcription is governed by three alternative promoters, all of which are negatively regulated by PPARγ.

Alternative promoter; Chicken; PGC-1α; PPARγ; Transcriptional regulation.