The Role of Mediator Subunit MED30 in Licensing the c-Myc Oncogenic Program [ChIP-seq]

Despite extensive functional and structural investigation of the Mediator complex, the basis for selective functional requirements for specific Mediator subunits for the actions of specific DNA binding transcription factors remain incompletely understood. Here, we report the MED30 subunit of Mediator, one of the core subunits maintaining the complex, plays a critical role in regulating the MYC transcription program in cancer cells. This is consequent to MED30 being required for stabilizing Mediator complex and MYC binding on the genome, involving low-affinity hydrophobic interaction functions of the MYC N-terminal Intrinsic Disordered Region (IDR). A mutational screen reveals that mutations in critical residues in the MYC coiled-coil domain structurally adjacent to the IDR of MED30 strongly inhibit tumor growth, even in the presence of wild-type MED30, mimicking the effects of MED30 deletion. This study provides new insights into the principles governing the Mediator complex actions MYC-related biological processes. Overall design: To map the binding sites of Mediator component MED17, MED30 and MYC, these factors ChIP-seq were performed in Mia PaCa-2 cells with antibodies MED17 (invitrogen PA5-30314), MED30 (from Dr. Thomas G. Boyer, UT health San Antonio, homemade) and Myc (CST #9402), respectively. To test the effect of MED30 knockdown in Myc's binding, MYC ChIP-seq was perform with or without three days 0.5ug/ml Dox treatment in Dox-induced shMED30 Mia PaCa-2 cells. To test the domain/motif contribution to binding for Myc, letivrus vector expressing HA-tagged Myc fragment and WT in Dox-induced manner were intergrated into Mia PaCa-2 cells, and 0.5ug/ml Dox was administrated for 1 day, another WT sample was not treated with Dox, serving as negative control.