TGF-β Induces Acetylation of Chromatin and of Ets-1 to Alleviate Repression of miR-192 in Diabetic Nephropathy

MicroRNAs (miRNAs), such as miR-192, mediate the actions of transforming growth factor-beta 1 (TGF-beta) related to the pathogenesis of diabetic kidney diseases. We found that the biphasic induction of miR-192 expression by TGF-beta in mouse renal glomerular mesangial cells initially involved the Smad transcription factors, followed by sustained expression that was promoted by acetylation of the transcription factor Ets-1 and of histone H3 by the acetyltransferase p300, which was activated by the serine and threonine kinase Akt. In mesangial cells from Ets-1-deficient mice or in cells in which Ets-1 was knocked down, basal amounts of miR-192 were higher than those in control cells, but sustained induction of miR-192 by TGF-beta was attenuated. Furthermore, inhibition of Akt or ectopic expression of dominant-negative histone acetyltransferases decreased p300-mediated acetylation and Ets-1 dissociation from the miR-192 promoter and prevented miR-192 expression in response to TGF-beta. Activation of Akt and p300 and acetylation of Ets-1 and histone H3 were increased in glomeruli from diabetic db/db mice compared to non-diabetic db/+ mice, suggesting that this pathway may contribute to diabetic nephropathy. These findings provide insight into the regulation of miRNAs through signaling-mediated changes in transcription factor activity and in epigenetic histone acetylation under normal and disease states.