HDAC8 cooperates with SMAD3/4 complex to suppress SIRT7 and promote cell survival and migration.

NAD(+)-dependent SIRT7 deacylase plays essential roles in ribosome biogenesis, stress response, genome integrity, metabolism and aging, while how it is transcriptionally regulated is still largely unclear. TGF-beta signaling is highly conserved in multicellular organisms, regulating cell growth, cancer stemness, migration and invasion. Here, we demonstrate that histone deacetylase HDAC8 forms complex with SMAD3/4 heterotrimer and occupies SIRT7 promoter, wherein it deacetylates H4 and thus suppresses SIRT7 transcription. Treatment with HDAC8 inhibitor compromises TGF-beta signaling via SIRT7-SMAD4 axis and consequently, inhibits lung metastasis and improves chemotherapy efficacy in breast cancer. Our data establish a regulatory feedback loop of TGF-beta signaling, wherein HDAC8 as a novel cofactor of SMAD3/4 complex, transcriptionally suppresses SIRT7 via local chromatin remodeling and thus further activates TGF-beta signaling. Targeting HDAC8 exhibits therapeutic potential for TGF-beta signaling related diseases.