Novel domains in chromodomain helicase binding protein 8

Chromodomain helicase binding protein 8 (Chd8) is a nuclear protein that regulates transcription and cell survival. Chd8 exists in large protein complexes and may act as a scaffold that coordinates multiple pathways to transcription. The objectives of this study are to 1) identify Chd8 as a novel A‐kinase anchoring protein (AKAP) and 2) show that this AKAP domain is required for Chd8‐mediated regulation of transcription. Phage display screening with the regulatory II (RII) subunit of protein kinase A (PKA) of human heart cDNA identified a novel PKA binding domain in Chd8. The amino terminus of Chd8 contains an amphipathic alpha helix similar to that found in AKAPs. Recombinant RII bound this region in RII overlay experiments. An amino terminal fragment of Chd8 co‐immunoprecipitated with RII‐CFP. These data indicate Chd8 is a novel nuclear AKAP. Co‐immunoprecipitation with endogenous proteins has identified another binding factor for Chd8. Duplin, a small splice variant of Chd8, binds and inhibits STAT3. We found that STAT3 co‐immunoprecipitated with full‐length Chd8 in HeLa cells. We predict that altered PKA binding to Chd8 in response to increased cAMP regulates interaction of Chd8 and STAT3 and alters activation of gene transcription. This work is supported by T32 HL072751, F31AG032162, and R01 AG16613.