Contrasting mammalian PTH promoters: identification of transcription factors controlling PTH gene expression.

Parathyroid hormone (PTH) is a key component in the maintenance of calcium and phosphate homeostasis. The steady-state expression of the PTH gene can be modeled as a balance between transcriptional activators and repressors. During renal failure, the gradual loss of kidney function is often accompanied by increased circulating concentrations of PTH and decreased synthesis of 1,25-di-hydroxyvitamin D3 (1,25(OH)2D3). The latter finding results in impaired calcium absorption and the removal of a known repressor of PTH gene transcription. Current regimens for treating secondary hyperparathyroidism associated with renal insufficiency are focused on boosting activities that repress PTH gene transcription or secretion of the hormone, and involve the use of vitamin D and its analogues or calcimimetic agents. However, in recent years, concerns have arisen over the use of the steroid hormone and alternative treatments are being sought. Here, we present new information regarding transcription factors controlling PTH gene expression, which include the specificity proteins (Sp) and the nuclear factor Y (NF-Y) complex. A highly conserved DNA response element for the Sp proteins has been identified in mammalian promoters, while an NF-Y binding site is uniquely positioned in the human promoter. Both of these factors are expressed in the parathyroid gland and their DNA elements appear to be functioning as activators of PTH gene expression. Further elucidation of such pathways may offer novel approaches for treating hyperparathyroidism associated with renal failure via suppression of transcriptional activators. That work is currently in progress.