Rescue of hypoxia-induced EMT in TET1 knockdown cells by a catalytically inactive TET1 mutant, and a model to depict the discovery of this report. (a,b) Expression of the TET1-CDmt expression vector in FADU (a) or H1299 (b) cells with TET1 knockdown restored the phenotype of hypoxia-induced EMT. (c) The model of TET1 serving as a 5mC dioxygenase and transcription activator. Red arrow indicates the process of demethylation of 5mC by TET1. TAD: transactivation domain of HIF-1α; CXXC: CXXC domain of TET1 protein; CD: catalytic domain of TET1 protein; meC: 5-methylcytosine; me: methyl group; HRE: hypoxia-response element.