Ets-2 interacts with co-repressor BS69 to repress target gene expression.

BACKGROUND: The ETS-family of proteins consists of over 30 members that regulate the growth, differentiation and survival of both normal and tumor cells. How specificity is achieved within this family remains largely unresolved. One mechanism for attaining specificity is through the action of signaling pathways on specific family members. For example, Ets-2 is an activator modulated by ras-dependent phosphorylation of a single residue in the conserved pointed domain of this factor. We hypothesized that phosphorylation of the pointed domain regulates the proteins that can interact with ets-2 in the cell nucleus, resulting in regulation of target genes. MATERIALS AND METHODS: We used a combination of biochemical assays, yeast two-hybrid screens and transfection assays to identify and characterize proteins interacting with the pointed domain. RESULTS: BS69, a known co-repressor, was identified in a yeast two hybrid screen as an ets-2 interacting partner. BS69 can interact with ets-2 in vivo and phosphorylation of the ets-2 pointed domain decreased the interaction with BS69 in vitro. In transfection assays, co-expression of ets-2 and BS69 resulted in repression of defined ets-2 target genes. CONCLUSION: These results support a role for ets-2 as a repressor and indicate that BS69 is required as co-repressor. Phosphorylation of ets-2 may switch its activity from repressor to activator by interfering with formation of the BS69 complex.

Ets-2 and components of mammalian SWI/SNF form a repressor complex that negatively regulates the BRCA1 promoter.

Ets-2 is a transcriptional activator that can be modulated by ras-dependent phosphorylation. Evidence is presented indicating that ets-2 can also act as a transcriptional repressor. In the breast cancer cell line MCF-7, exogenous ets-2 repressed the activity of a BRCA1 promoter-luciferase reporter dependent on a conserved ets-2-binding site in this promoter. Conditional overproduction of ets-2 in MCF-7 cells resulted in repression of endogenous BRCA1 mRNA expression. To address the mechanism by which ets-2 could act as a repressor, a biochemical approach was used to identify proteins that interacted with the ets-2 pointed domain. From this analysis, components of the mammalian SWI/SNF chromatin remodeling complex were found to interact with ets-2. Brg-1, the ATP-hydrolyzing component of the SWI/SNF complex, along with the BAF57/p50 and Ini1 subunits could be co-immunoprecipitated from cells with ets-2. The pointed domain of ets-2 directly interacted in vitro with the C-terminal region of Brg-1 in a phosphorylation-dependent manner. The combination of Brg-1 and ets-2 could repress the BRCA1 promoter reporter in transfection assays. These results support a role for ets-2 as a repressor and indicate that components of the mammalian SNF/SWI complex are required as co-repressors.