Identification of Novel Domains within Sox-2 and Sox-11 Involved in Autoinhibition of DNA Binding and Partnership Specificity

Abstract

Sox transcription factors play key regulatory roles throughout development, binding DNA through a consensus (A/T)(A/T)CAA(A/T)G sequence. Although many different Sox proteins bind to this sequence, it has been observed that gene regulatory elements are commonly responsive to only a small subset of the entire family, implying that regulatory mechanisms exist to permit selective DNA binding and/or transactivation by Sox family members. To identify and explore the mechanisms modulating gene activation by Sox proteins further, we compared the function of Sox-2 and Sox-11. This led to the discovery that Sox proteins are regulated differentially at multiple levels, including transactivation, protein partnerships with Pit-Oct-Unc (POU) transcription factors, and DNA binding autoregulation. Specifically, we determined that Sox-11 activates transcription more strongly than Sox-2 and that the transactivation domain of Sox-11 is primarily responsible for this capability. Additionally, we demonstrate that the Sox-11 DNA binding domain is responsible for selective cooperation with the POU factor Brn-2. This requirement cannot be replaced by the DNA binding domain of Sox-2, indicating that the DNA binding domain of Sox proteins is critical for Sox-POU partnerships. Interestingly, we have also determined that a conserved domain of Sox-11 has the novel capability of autoinhibiting its ability to bind DNA in vitro and to activate gene expression in vivo. Our findings suggest that the autoinhibitory domain can repress promiscuous binding of Sox-11 to DNA and plays an important role in regulating the recruitment of Sox-11 to specific genes.

Nuclear expression of the non–B-cell lineage Sox11 transcription factor identifies mantle cell lymphoma

“…It was shown that both proteins cooperated with Oct-3, while only Sox11 could partner with Brn-2 to activate transcription. 26 Brn-2 is involved in the proliferation of melanoma cells and can, like cyclin D1, be induced by the WNT/Beta-catenin pathway. 27 In the murine system, it has been shown in primary and continuous cell cultures that neuron survival and neurite growth are dependent on Sox11.…”

Sox proteins: regulators of cell fate specification and differentiation

“…Similarly, the sequences bound by Sox9 dimers found in the enhancers of genes associated with chondrocyte development, e.g. those for collagens, deviate considerably from the Sox consensus binding (Wiebe et al, 2003), Sox2 (Tomioka et al, 2002), Utf1 (Nishimoto et al, 1999), nestin (Nes) (Tanaka et al, 2004). In contrast to the heterodimers, the Sox9 dimer-binding sequences deviate from the Sox consensus in both sites (Bernard et al, 2003;Bridgewater et al, 2003;Dy et al, 2012;Han and Lefebvre, 2008;Sock et al, 2003).…”

The Optimedin Gene Is a Downstream Target of Pax6

“…Sox11 but not Sox2 stimulated the reporter construct in transfection experiments, but only Sox2 was capable of binding to the putative binding site as judged by the EMSA. The authors suggested that there is a domain in the Sox11 protein that has a capability of autoinhibiting its ability to bind DNA in vitro and to activate gene expression in vivo (41). This suggestion may also explain the results we obtained with the Optimedin promoter.…”

“…Sox2, Sox11, and Brn1 cDNAs were cloned into the pCMV5 expression vector (41,42) and were kindly provided by Drs. A. Rizzino (University of Nebraska) and D. Robbins (University of Michigan), respectively.…”