ZNF76, a novel transcriptional repressor targeting TATA-binding protein, is modulated by sumoylation

Direct interaction of positive and negative regulators with the general transcription machinery modulates transcription. The TATA-binding protein (TBP) is one target for transcriptional regulators. In this study, we identified ZNF76 as a novel transcriptional repressor that targets TBP. ZNF76 interacts with TBP through both its N and C termini, and both regions are required for ZNF76 to exert its inhibitory function on p53-mediated transactivation. The inhibitory effect of ZNF76 on p53 activity was demonstrated by reporter assays and endogenous target gene expression. We mapped the TBP-interacting region in the C terminus of ZNF76 to a glutamic acid-rich domain, which acts in a dominant negative manner to enhance p53-mediated transactivation in reporter assays. Mutagenesis study for ZNF76 suggests a correlation between interaction with TBP and effect on p53-mediated transactivation, supporting the conclusion that ZNF76 targets TBP for transcriptional repression. Chromatin immunoprecipitation experiments suggest that ZNF76 prevents TBP from occupying the endogenous p21 promoter. ZNF76 is sumoylated by PIAS1 at lysine 411, which is in the minimal TBP-interacting region. Overexpression of PIAS1 and SUMO-1 abolishes the interaction between ZNF76 and TBP and partially relieves the repressive effect of ZNF76. These results suggest that ZNF76 functions as a transcriptional repressor through its interaction with TBP and that sumoylation modulates its transcriptional repression activity.