Functional Characterization of Exonic Variants of the PPARGC1B Gene in Coregulation of Estrogen Receptor Alpha

Abstract

Peroxisome proliferator-activated receptor gamma coactivator 1 beta (PPARGC1B) is a coactivator of estrogen receptor (ER)alpha and ER beta. We previously demonstrated a significant association between a variant of exon 5 of the PPARGC1B gene (+102525 G>A, R265Q) and airway hyperreactivity (AHR). The aims of the study were to evaluate the genetic effects of variants of the PPARGC1B gene on the function of ERs. PPARGC1B +102525G and A gene constructs were generated using PCR and cloned into a pCMV4 promoter vector. A luciferase reporter assay was undertaken in 293T cells cotransfected with one of the PPARGC1B +102525G>A constructs, ER alpha, and an estrogen response element (ERE) containing a luciferase construct after treatment with 17 beta-estradiol. According to the luciferase reporter assay, the +102525A allele showed higher ER alpha activity than the +102525G allele in response to stimulation with 17 beta-estradiol. In addition, the interaction between ER alpha and PPARGC1B was evaluated by coprecipitation assay. Human influenza hemagglutinin-tagged PPARGC1B co-precipitated more intensely with ER alpha in the +102525A than the +102525G construct after 17 beta estradiol treatment. The variant +102525A allele enhances the activity of ER alpha to a greater degree than the +102525G allele of PPARGC1B.