Transcriptional Coactivator, CIITA, Is an Acetyltransferase that Bypasses a Promoter Requirement for TAF II250

Abstract

The CIITA coactivator is essential for transcriptional activation of MHC class II genes and mediates enhanced MHC class I transcription. We now report that CIITA contains an intrinsic acetyltransferase (AT) activity that maps to a region within the N-terminal segment of CIITA, between amino acids 94 and 132. The AT activity is regulated by the C-terminal GTP-binding domain and is stimulated by GTP. CIITA-mediated transactivation depends on the AT activity. Further, we report that, although constitutive MHC class I transcription depends on TAF II250, CIITA activates the promoter in the absence of functional TAF II250.