A commonly occurring polymorphism upstream of the estrogen receptor alpha alters transcription and is associated with increased HDL.

OBJECTIVE: Given the role of estrogen in the regulation of lipid metabolism, we screened for functional polymorphisms in the estrogen receptor alpha (ER*), and examined for their influence on serum cholesterol. METHODS AND RESULTS: We identified a novel C>T polymorphism (ERNE-145), with a minor allele frequency of 41%. This polymorphism was immediately adjacent to a putative glucocorticoid receptor (GR) binding site, which we showed to be functional by electrophoretic mobility shift analysis. The C allele was associated with glucocorticoid-induced reduction in promoter activity compared to control in luciferase reporter studies (p<0.05; n=7). This effect was abolished by the T allele. To investigate the functional significance of ERNE-145, its association with serum cholesterol levels was examined in 1662 post-menopausal women enrolled in the RUTH trial. ERNE-145 genotype (p=0.001), BMI (p<0.001), diabetes mellitus (p<0.001), and ethnicity (p=0.002) were significantly associated with HDL cholesterol. ERNE-145 genotype explained 8.2% of the variability of HDL: each copy of the variant T allele was associated with a 0.041 mmol/L (CI 0.017-0.066) increase in HDL. CONCLUSION: A novel polymorphism upstream of ER* abolished negative transcriptional regulation by an adjacent GR binding sequence, and was strongly associated with HDL levels in a large cohort of post-menopausal women.

PAX8-peroxisome proliferator-activated receptor gamma (PPARgamma) disrupts normal PAX8 or PPARgamma transcriptional function and stimulates follicular thyroid cell growth.

Follicular thyroid carcinomas are associated with a chromosomal translocation that fuses the thyroid-specific transcription factor paired box gene 8 (PAX8) with the nuclear receptor peroxisome proliferator-activated receptor gamma (PPARgamma). This study investigated the transcriptional mechanisms by which PAX8-PPARgamma regulates follicular thyroid cells. In HeLa cells, rat follicular thyroid (FRTL-5) cells, or immortalized human thyroid cells, PAX8-PPARgamma stimulated transcription from PAX8-responsive thyroperoxidase and sodium-iodide symporter promoters in a manner at least comparable with wild-type PAX8. In contrast, PAX8-PPARgamma failed to stimulate transcription from the thyroglobulin promoter and blocked the synergistic stimulation of this promoter by wild-type PAX8 and thyroid transcription factor-1. Unexpectedly, PAX8-PPARgamma transcriptional function on a PPARgamma-responsive promoter was cell-type dependent; in HeLa cells, PAX8-PPARgamma dominantly inhibited expression of the PPARgamma-responsive promoter, whereas in FRTL-5 and immortalized human thyroid cells PAX8-PPARgamma stimulated this promoter. In gel shift analyses, PAX8-PPARgamma bound a PPARgamma-response element suggesting that its transcriptional function is mediated via direct DNA contact. A biological model of PAX8-PPARgamma function in follicular thyroid cells was generated via constitutive expression of the fusion protein in FRTL-5 cells. In this model, PAX8-PPARgamma expression was associated with enhanced growth as assessed by soft agar assays and thymidine uptake. Therefore, PAX8-PPARgamma disrupts normal transcriptional regulation by stimulating some genes and inhibiting others, the net effect of which may mediate follicular thyroid cell growth and loss of differentiation that ultimately leads to carcinogenesis.