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[摘要]：Proteomic analyses have contributed substantially to our understanding of diverse cellular processes. Improvements in the sensitivity of mass spectrometry approaches are enabling more in-depth analyses of protein-protein networks and, in some cases, are providing surprising new insights into well established, longstanding problems. Here, we describe such a proteomic analysis that exploits MudPIT mass spectrometry and has led to the discovery of a physical and functional link between the orphan nuclear receptor hepatocyte nuclear factor 4 alpha (HNF4 alpha) and transcription factor IID (TFIID). A systematic characterization of the HNF4 alpha-TFIID link revealed that the HNF4 alpha DNA-binding domain binds directly to the TATA box-binding protein (TBP) and, through this interaction, can target TBP or TFIID to promoters containing HNF4 alpha-binding sites in vitro. Supporting the functional significance of this interaction, an HNF4 alpha mutation that blocks binding of TBP to HNF4 alpha interferes with HNF4 alpha transactivation activity in cells. These findings identify an unexpected role for the HNF4 alpha DNA-binding domain in mediating key regulatory interactions and provide new insights into the roles of HNF4 alpha and TFIID in RNA polymerase II transcription. |
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