The DNA Binding Activities of Smad2 and Smad3 Are Regulated by Coactivator-mediated Acetylation
Ludwig Institute for Cancer Research, Uppsala University, Biomedical Center, Box 595, Husargatan 3, S-751 24 Uppsala, Sweden. Journal of Biological Chemistry
(Impact Factor: 4.57).
01/2007; 281(52):39870-80. DOI: 10.1074/jbc.M607868200
Phosphorylation-dependent activation of the transcription factors Smad2 and Smad3 plays an important role in TGFbeta-dependent signal transduction. Following phosphorylation of Smad2 and Smad3, these molecules are translocated to the nucleus where they interact with coactivators and/or corepressors, including p300, CBP, and P/CAF, and regulate the expression of TGFbeta target genes. In the current study, we demonstrate that both Smad2 and Smad3 are acetylated by the coactivators p300 and CBP in a TGFbeta-dependent manner. Smad2 is also acetylated by P/CAF. The acetylation of Smad2 was significantly higher than that of Smad3. Lys(19) in the MH1 domain was identified as the major acetylated residue in both the long and short isoform of Smad2. Mutation of Lys(19) also reduced the p300-mediated acetylation of Smad3. By generating acetyl-Lys(19)-specific antibodies, we demonstrate that endogenous Smad2 is acetylated on this residue in response to TGFbeta signaling. Acetylation of the short isoform of Smad2 improves its DNA binding activity in vitro and enhances its association with target promoters in vivo, thereby augmenting its transcriptional activity. Acetylation of Lys(19) also enhanced the DNA binding activity of Smad3. Our data indicate that acetylation of Lys(19) induces a conformational change in the MH1 domain of the short isoform of Smad2, thereby making its DNA binding domain accessible for interactions with DNA. Thus, coactivator-mediated acetylation of receptor-activated Smad molecules could represent a novel way to regulate TGFbeta signaling.
Available from: Suzanne L Advani
- "Canonical TGF-β1 signaling involves the receptor activated Smad proteins (Smad2 and Smad3), which, upon phosphorylation, associate with Smad4, translocate to the nucleus and act as transcription factors [41,51,52]. However recent data demonstrates that a further level of transcriptional regulation is necessary to mediate TGF-β downstream signaling, involving Smad acetylation [28,29,42]. Indeed, it has come to be appreciated that the post translational modifications of proteins by acetylation and de-acetylation is ubiquitous, comparable to other well described post translational modifications as a key regulator of protein and therefore cell function [19,43]. "
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Despite advances in the treatment of heart failure, mortality remains high, particularly in individuals with diabetes. Activated transforming growth factor beta (TGF-β) contributes to the pathogenesis of the fibrotic interstitium observed in diabetic cardiomyopathy. We hypothesized that high glucose enhances the activity of the transcriptional co-activator p300, leading to the activation of TGF-β via acetylation of Smad2; and that by inhibiting p300, TGF-β activity will be reduced and heart failure prevented in a clinically relevant animal model of diabetic cardiomyopathy.
p300 activity was assessed in H9c2 cardiomyoblasts under normal glucose (5.6 mmol/L—NG) and high glucose (25 mmol/L—HG) conditions. 3H-proline incorporation in cardiac fibroblasts was also assessed as a marker of collagen synthesis. The role of p300 activity in modifying TGF-β activity was investigated with a known p300 inhibitor, curcumin or p300 siRNA in vitro, and the functional effects of p300 inhibition were assessed using curcumin in a hemodynamically validated model of diabetic cardiomyopathy – the diabetic TG m(Ren-2)27 rat.
In vitro, H9c2 cells exposed to HG demonstrated increased p300 activity, Smad2 acetylation and increased TGF-β activity as assessed by Smad7 induction (all p < 0.05 c/w NG). Furthermore, HG induced 3H-proline incorporation as a marker of collagen synthesis (p < 0.05 c/w NG). p300 inhibition, using either siRNA or curcumin reduced p300 activity, Smad acetylation and TGF-β activity (all p < 0.05 c/w vehicle or scrambled siRNA). Furthermore, curcumin therapy reduced 3H-proline incorporation in HG and TGF-β stimulated fibroblasts (p < 0.05 c/w NG). To determine the functional significance of p300 inhibition, diabetic Ren-2 rats were randomized to receive curcumin or vehicle for 6 weeks. Curcumin treatment reduced cardiac hypertrophy, improved diastolic function and reduced extracellular matrix production, without affecting glycemic control, along with a reduction in TGF-β activity as assessed by Smad7 activation (all p < 0.05 c/w vehicle treated diabetic animals).
These findings suggest that high glucose increases the activity of the transcriptional co-regulator p300, which increases TGF-β activity via Smad2 acetylation. Modulation of p300 may be a novel strategy to treat diabetes induced heart failure.
Cardiovascular Diabetology 05/2014; 13(1):89. DOI:10.1186/1475-2840-13-89 · 4.02 Impact Factor
Available from: Kyung-Chul Choi
- "Recent studies demonstrated that acetylation targets Smad2 and Smad3 to the Smad binding site of EMT target genes, including PAI-1, Snail, and Slug, in a TGF-b1-dependent manner . To investigate the role of acetylation in Smad2 and Smad3 recruitment to the PAI-1 promoter, we performed ChIP assays in TGF- b1-stimulated A549 cells (Fig. 6A). "
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ABSTRACT: Transforming growth factor-β1, the key ligand of Smad-dependent signaling pathway, is critical for epithelial-mesenchymal transition during embryo-morphogenesis, fibrotic diseases, and tumor metastasis. In this study, we found that activation of p300/CBP, a histone acetyltransferase, by TGF-β1 mediates Epithelial-mesenchymal transition (EMT) via acetylating Smad2 and Smad3 in TGF-β1 signaling pathway. We demonstrated that treatment with EGCG inhibited p300/CBP activity in human lung cancer cells. Also, we observed that EGCG potently inhibited TGF-β1-induced EMT and reversed the up-regulation of various genes during EMT. Our findings suggest that EGCG inhibits the induction of p300/CBP activity by TGF-β1. Therefore, EGCG inhibits TGF-β1-mediated EMT by suppressing the acetylation of Smad2 and Smad3 in human lung cancer cells.
Cancer letters 02/2013; 335(1). DOI:10.1016/j.canlet.2013.02.018 · 5.62 Impact Factor
Available from: Jean-Jacques Lebrun
- "Moreover, the acetylation is specific to Smad2 and Smad3, as p21 did not show any increased acetylation by p/CAF (data not shown). Smad3 acetylation has been suggested to be required for its DNA binding activity . Thus, this led us to investigate whether p/CAF could associate with DNA-bound Smad3, by DNA immunoprecipitation (DNA IP) using biotinylated control and biotinylated Smad binding element (4× CAGA) DNA probes. "
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Tumor cell migration and invasion are critical initiation steps in the process of breast cancer metastasis, the primary cause of breast cancer morbidity and death. Here we investigated the role of p21Cip1 (p21), a member of the core cell cycle machinery, in transforming growth factor-beta (TGFβ)-mediated breast cancer cell migration and invasion.
A mammary fat pad xenograft mouse model was used to assess the mammary tumor growth and local invasion. The triple negative human breast cancer cell lines MDA-MB231 and its sub-progenies SCP2 and SCP25, SUM159PT, SUM149PT, SUM229PE and SUM1315MO2 were treated with 5 ng/ml TGFβ and the protein expression levels were measured by Western blot. Cell migration and invasion were examined using the scratch/wound healing and Transwell assay. TGFβ transcriptional activity was measured by a TGFβ/Smad reporter construct (CAGA12-luc) using luciferase assay. q-PCR was used for assessing TGFβ downstream target genes. The interactions among p21, p/CAF and Smad3 were performed by co-immunoprecipitation. In addition, Smad3 on DNA binding ability was measured by DNA immunoprecipitation using biotinylated Smad binding element DNA probes. Finally, the association among active TGFβ/Smad signaling, p21 and p/CAF with lymph node metastasis was examined by immunohistochemistry in tissue microarray containing 50 invasive ductal breast tumors, 25 of which are lymph node positive.
We found p21 expression to correlate with poor overall and distant metastasis free survival in breast cancer patients. Furthermore, using xenograft animal models and in vitro studies, we found p21 to be essential for tumor cell invasion. The invasive effects of p21 were found to correlate with Smad3, and p/CAF interaction downstream of TGFβ. p21 and p/CAF regulates TGFβ-mediated transcription of pro-metastatic genes by controlling Smad3 acetylation, DNA binding and transcriptional activity. In addition, we found that active TGFβ/Smad signaling correlates with high p21 and p/CAF expression levels and lymph node involvement using tissue microarrays from breast cancer patients.
Together these results highlight an important role for p21 and p/CAF in promoting breast cancer cell migration and invasion at the transcriptional level and may open new avenues for breast cancer therapy.
Breast cancer research: BCR 09/2012; 14(5):R127. DOI:10.1186/bcr3322 · 5.49 Impact Factor
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