Different domains of the transcription factor ELF3 are required in a promoter-specific manner and multiple domains control its binding to DNA.

Elf3 is an epithelially restricted member of the ETS transcription factor family, which is involved in a wide range of normal cellular processes. Elf3 is also aberrantly expressed in several cancers, including breast cancer. To better understand the molecular mechanisms by which Elf3 regulates these processes, we created a large series of Elf3 mutant proteins with specific domains deleted or targeted by point mutations. The modified forms of Elf3 were used to analyze the contribution of each domain to DNA binding and the activation of gene expression. Our work demonstrates that three regions of Elf3, in addition to its DNA binding domain (ETS domain), influence Elf3 binding to DNA, including the transactivation domain that behaves as an autoinhibitory domain. Interestingly, disruption of the transactivation domain relieves the autoinhibition of Elf3 and enhances Elf3 binding to DNA. On the basis of these studies, we suggest a model for autoinhibition of Elf3 involving intramolecular interactions. Importantly, this model is consistent with our finding that the N-terminal region of Elf3, which contains the transactivation domain, interacts with its C terminus, which contains the ETS domain. In parallel studies, we demonstrate that residues flanking the N- and C-terminal sides of the ETS domain of Elf3 are crucial for its binding to DNA. Our studies also show that an AT-hook domain, as well as the serine- and aspartic acid-rich domain but not the pointed domain, is necessary for Elf3 activation of promoter activity. Unexpectedly, we determined that one of the AT-hook domains is required in a promoter-specific manner.