Upregulation of human with-no-lysine kinase-4 gene expression by GATA-1 acetylation

With-no-lysine kinase-4 (WNK4), a member of the serine-threonine protein kinase family, acts as a multifunctional regulator of diverse ion transporters. Therefore, it is interesting to investigate the mechanisms that control its expression. We have previously demonstrated that glucocorticoid downregulates human WNK4 (hWNK4) expression through the negative glucocorticoid responsive element. Here, using real-time PCR and Western blot assays, we show that trichostatin A (TSA), a histone deacetylase inhibitor, upregulated hWNK4 mRNA and protein expression in human embryo kidney 293 cells. Analysis of the transcriptional activity of a series of the truncated hWNK4 promoters by luciferase assay indicated that the region −484 to −337 of the hWNK4 promoter was sensitive to TSA, and a GATA-1 binding motif was identified at position −426 using TRANSFAC-TESS program. Moreover, using electrophoresis mobility shift assay and chromatin immunoprecipitation assay, the GATA-1 binding affinity to the hWNK4 promoter was shown to increase with TSA under in vitro and in vivo conditions. Immunoprecipitation and Western blot analyses showed that the levels of acetylated GATA-1 were increased with TSA, in agreement with changes in its DNA-binding affinity. These findings indicate that TSA induces hWNK4 expression, at least in part, by increasing GATA-1 acetylation, and thereby its binding to the GATA-1 responsive element, within the hWNK4 promoter.