Aldosterone-sensitive Repression of ENaCα Transcription by A Histone H3 Lysine-79 Methyltransferase

Zhang, Wenzheng, Xuefeng Xia, Diana I. Jalal, Teresa Kuncewicz, William Xu, Gene D. Lesage, and Bruce C. Kone. Aldosterone-sensitive repression of ENaC transcription by a histone H3 lysine-79 methyltransferase. Am J Physiol Cell Physiol 290: C936–C946, 2006. First published October 19, 2005; doi:10.1152/ajpcell.00431.2005.—Aldosterone is a major regulator of epithelial Na absorption. One of its principal targets is the epithelial Na channel -subunit (ENaC ), principally expressed in the kidney collecting duct, lung, and colon. Models of aldosterone-mediated trans-activation of the ENaC gene have focused primarily on interactions of liganded nuclear receptors with the ENaC gene promoter. Herein, we demonstrate that the murine histone H3 lysine-79 methyltransferase, murine disruptor of telomeric silencing alternative splice variant “a” (mDot1a), is a novel component in the aldosterone signaling network controlling transcription of the ENaC gene. Aldosterone downregulated mDot1a mRNA levels in murine inner medullary collecting ducts cells, which was associated with histone H3 K79 hypomethylation in bulk histones and at specific sites in the ENaC 5 -flanking region, and trans-activation of ENaC . Knockdown of mDot1a by RNA interference increased activity of a stably integrated ENaC promoter-luciferase construct and expression of endogenous ENaC mRNA. Conversely, overexpression of EGFP-tagged mDot1a resulted in hypermethylation of histone H3 K79 at the endogenous ENaC promoter, repression of endogenous ENaC mRNA expression, and decreased activity of the ENaC promoter-luciferase construct. mDot1a-mediated histone H3 K79 hypermethylation and repression of ENaC promoter activity was abolished by mDot1a mutations that eliminate its methyltransferase activity. Collectively, our data identify mDot1a as a novel aldosteroneregulated histone modification enzyme, and, through binding the ENaC promoter and hypermethylating histone H3 K79 associated with the ENaC promoter, a negative regulator of ENaC transcription.