Aldosterone-induced Sgk1 relieves Dot1a-Af9–mediated transcriptional repression of epithelial Na+ channel α
Wenzheng Zhang, … , Volker Vallon, Bruce C. Kone
Wenzheng Zhang, … , Volker Vallon, Bruce C. Kone
Published March 1, 2007
Citation Information: J Clin Invest. 2007;117(3):773-783. https://doi.org/10.1172/JCI29850.
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Research Article

Aldosterone-induced Sgk1 relieves Dot1a-Af9–mediated transcriptional repression of epithelial Na+ channel α

Abstract

Aldosterone plays a major role in the regulation of salt balance and the pathophysiology of cardiovascular and renal diseases. Many aldosterone-regulated genes — including that encoding the epithelial Na+ channel (ENaC), a key arbiter of Na+ transport in the kidney and other epithelia — have been identified, but the mechanisms by which the hormone modifies chromatin structure and thus transcription remain unknown. We previously described the basal repression of ENaCα by a complex containing the histone H3 Lys79 methyltransferase disruptor of telomeric silencing alternative splice variant a (Dot1a) and the putative transcription factor ALL1-fused gene from chromosome 9 (Af9) as well as the release of this repression by aldosterone treatment. Here we provide evidence from renal collecting duct cells and serum- and glucocorticoid-induced kinase–1 (Sgk1) WT and knockout mice that Sgk1 phosphorylated Af9, thereby impairing the Dot1a-Af9 interaction and leading to targeted histone H3 Lys79 hypomethylation at the ENaCα promoter and derepression of ENaCα transcription. Thus, Af9 is a physiologic target of Sgk1, and Sgk1 negatively regulates the Dot1a-Af9 repressor complex that controls transcription of ENaCα and likely other aldosterone-induced genes.

Authors

Wenzheng Zhang, Xuefeng Xia, Mary Rose Reisenauer, Timo Rieg, Florian Lang, Dietmar Kuhl, Volker Vallon, Bruce C. Kone

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Figure 3

Sgk1 impairs Af9 interaction with Dot1a in vitro.

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Sgk1 impairs Af9 interaction with Dot1a in vitro. (A) GST pulldown assay...
(A) GST pulldown assay showing impaired ability of Sgk1-phosphorylated Af9 to retain the EGFP-Dot1a fusion. As in Figure 1C, GST-Af9 397–557 was phosphorylated by Sgk1 and incubated with mIMCD3 cell lysates containing EGFP-Dot1a 479–659. Bound proteins were examined by IB with the indicated antibodies (n = 3). (B) As in A, except for inclusion of GST-Af9 Ser435Ala as control, increasing input volumes (μl) of EGFP-Dot1a 479–659 lysate and the indicated antibodies. The same mIMCD3 cell lysates (3 μl) were loaded in the far right lane. The amount of bound EGFP-Dot1a 479–659 was normalized to that of total GST-Af9 fusions to calculate the relative binding efficiency and were plotted, with the efficiency of the reaction GST-Af9 397–557, –Sgk1, at 100 μl of input lysate assigned as 1 (n = 3). *P < 0.05 versus corresponding GST-Af9 397–557, –Sgk1.