TGF-beta signalling through SMAD1/5 is required for epithelial-to-mesenchymal transition

TGF-beta treatment leads to SMAD1/5 phosphorylation. However, the ability of SMAD1/5 to bind chromatin downstream of TGF-beta signalling is unknown. We performed ChIP-sequencing for pSMAD1/5 and SMAD3 to identify binding sites for pSMAD1/5 upon TGF-beta stimulation and identified preferential pSMAD1/5 binding at SMAD1/5:SMAD4 consensus sites. MDA-MB-231 cells untreated or treated with TGF-beta for 1 h and then examined with a SMAD3 or pSMAD1/5 antibody. The SMAD3 acts as a control as it is well known that SMAD3 is required for transcriptional regulation of many TGF-beta target genes.