Physical and functional interactions between Daxx and DNA methyltransferase 1-associated protein, DMAP1

Daxx has been shown to play an essential role in type I IFN-alphabeta-mediated suppression of B cell development and apoptosis. Recently, we demonstrated that Tyk2 is directly involved in IFN signaling for the induction and translocation of Daxx, which may result in growth arrest and/or apoptosis of B lymphocyte progenitors. To clarify how Daxx regulates B cell development, we examined Daxx interacting partners by yeast two-hybrid screening. DNA methyltransferase 1 (DNMT1)-associated protein (DMAP1) was identified and demonstrated to interact with Daxx. The interaction regions in both proteins were mapped, and the cellular localization of the interaction was examined. Both Daxx and DMAP1 formed a complex with DNMT1 and colocalized in the nucleus. DMAP1 enhanced Daxx-mediated repression of glucocorticoid receptor transcriptional activity. Furthermore, Daxx protected protein degradation of DMAP1 in vivo. These results provide the novel molecular link between Daxx and DNMT1, which establishes a repressive transcription complex in the nucleus.