Transforming growth factor-? induces transcription factors MafK and Bach1 to suppress expression of the heme oxygenase-1 gene.

ABSTRACT: Transforming growth factor-? (TGF-?) has multiple functions in embryogenesis, adult homeostasis, tissue repair, and development of cancer. Here, we report that TGF-? suppresses the transcriptional activation of the heme oxygenase-1 (HO-1) gene, which is implicated in protection against oxidative injury and lung carcinogenesis. HO-1 is a target of the oxidative stress-responsive transcription factor Nrf2. TGF-? did not affect the stabilization or nuclear accumulation of Nrf2 after stimulation with electrophiles. Instead, TGF-? induced expression of transcription factors MafK and Bach1. Enhanced expression of either MafK or Bach1 was enough to suppress the electrophile-inducible expression of HO-1 even in the presence of accumulated Nrf2 in the nucleus. Knockdown of MafK and Bach1 by siRNA abolished TGF-?-dependent suppression of HO-1. Furthermore, chromatin immunoprecipitation assays revealed that Nrf2 substitutes for Bach1 at the antioxidant response elements (E1 and E2), which are responsible for the induction of HO-1 in response to oxidative stress. On the other hand, pretreatment with TGF-? suppressed binding of Nrf2 to both E1 and E2 but marginally increased the binding of MafK to E2 together with Smads. As TGF-? is activated after tissue injury and in the process of cancer development, these findings suggest a novel mechanism by which damaged tissue becomes vulnerable to oxidative stress and xenobiotics.

SUBMITTER: Okita Y 

PROVIDER: S-EPMC3711329 | biostudies-literature | 2013 Jul

REPOSITORIES: biostudies-literature