Association of Class I Histone Deacetylases with Transcriptional Corepressor CtBP

The C-terminal binding protein (CtBP) family proteins are transcriptional regulators that are conserved from worm to human. They function as corepressors of a wide array of DNA-binding transcriptional repressors. The mammalian CtBPs appear to mediate transcriptional repression in a histone deacetylase (HDAC)-dependent or -independent manner, depending on the context of the promoter. To identify the components of the CtBP corepressor complex, we isolated CtBP-containing protein complexes from the nuclear extracts prepared from HeLa cells infected with adenovirus vectors that expresses hCtBP1. Western blot analysis of these complexes suggests that hCtBP1 associates with class I HDACs, HDAC-1, HDAC-2 and HDAC-3. Some of these HDACs also interact with the Drosophila CtBP homolog, dCtBP. The CtBP protein complex exhibits significant HDAC activity in vitro suggesting that association of CtBP with HDACs may be functionally relevant.