ABSTRACT
TGF-ß signaling regulates a variety of cellular processes, including proliferation, apoptosis, differentiation, immune responses, and fibrogenesis. Here, we describe a lysine methylation-mediated mechanism that controls the pro-fibrogenic activity of TGF-ß. We find that the methyltransferase Set9 potentiates TGF-ß signaling by targeting Smad7, an inhibitory downstream effector. Smad7 methylation promotes interaction with the E3 ligase Arkadia and, thus, ubiquitination-dependent degradation. Depletion or pharmacological inhibition of Set9 results in elevated Smad7 protein levels and inhibits TGF-ß-dependent expression of genes encoding extracellular matrix components. The inhibitory effect of Set9 on TGF-ß-mediated extracellular matrix production is further demonstrated in mouse models of pulmonary fibrosis. Lung fibrosis induced by bleomycin or Ad-TGF-ß treatment was highly compromised in Set9-deficient mice. These results uncover a complex regulatory interplay among multiple Smad7 modifications and highlight the possibility that protein methyltransferases may represent promising therapeutic targets for treating lung fibrosis.
Subject(s)
Histone-Lysine N-Methyltransferase/metabolism , Protein Methyltransferases/metabolism , Pulmonary Fibrosis/metabolism , Signal Transduction , Transforming Growth Factor beta/metabolism , Acetylation , Animals , Bleomycin , Extracellular Matrix/genetics , Extracellular Matrix/metabolism , Gene Expression Regulation , HeLa Cells , Humans , Lysine/metabolism , Male , Methylation , Mice, Inbred C57BL , Mice, Knockout , Models, Biological , Nuclear Proteins/metabolism , Protein Stability , Pulmonary Fibrosis/genetics , Pulmonary Fibrosis/pathology , Signal Transduction/genetics , Smad7 Protein/metabolism , Ubiquitin-Protein Ligases/metabolism , Ubiquitination/geneticsABSTRACT
ATP-dependent chromatin remodeling is involved in all DNA transactions and is linked to numerous human diseases. We explored functions of chromatin remodelers during cellular aging. Deletion of ISW2, or mutations inactivating the Isw2 enzyme complex, extends yeast replicative lifespan. This extension by ISW2 deletion is epistatic to the longevity effect of calorie restriction (CR), and this mechanism is distinct from suppression of TOR signaling by CR. Transcriptome analysis indicates that isw2Δ partially mimics an upregulated stress response in CR cells. In particular, isw2Δ cells show an increased response to genotoxic stresses, and the DNA repair enzyme Rad51 is important for isw2Δ-mediated longevity. We show that lifespan is also extended in C. elegans by reducing levels of athp-2, a putative ortholog of Itc1/ACF1, a critical subunit of the enzyme complex. Our findings demonstrate that the ISWI class of ATP-dependent chromatin remodeling complexes plays a conserved role during aging and in CR.