Glucocorticoid repression of human with-no-lysine (K) kinase-4 gene expression is mediated by the negative response elements in the promoter

With-no-lysine (K) kinase-4 (WNK4) is a serine/threonine kinase that plays an essential role in the regulation of fluid and electrolyte homeostasis. The effects of glucocorticoids, key physiological regulators, on the WNK4 gene expression are still unknown. Here, we used dexamethasone (Dex) to treat the human embryo kidney 293 (HEK293) cells and found a decrease of human WNK4 (hWNK4) mRNA level by northern blot and real-time quantitative PCR. After an hWNK4 transcriptional initiation site was located by 5' rapid amplification of cDNA end assay, a series of 5'-deleted hWNK4 promoter-lucif erase constructs were generated by PCR. Transfection of these constructs in COS-7 and HEK293 cells revealed that Dex inhibited the hWNK4 transcriptional activity in glucocorticoid receptor (GR)-dependent pattern. Two negative glucocorticoid response elements (nGREs) were identified at -285 and -337 of the hWNK4 gene promoter and the GR binding activity to them was increased by Dex as shown by electrophoretic mobility shift assay and chromatin immunoprecipitation. In summary, these data demonstrated that hWNK4 was a new glucocorticoid-regulated gene whose expression was inhibited through the interaction of GR with nGREs in the promoter region.