Identification of novel domains within Sox-2 and Sox-11 involved in autoinhibition of DNA binding and partnership specificity.
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.
Wiebe
Matthew S
MS
Eppley Institute for Research in Cancer and Allied Diseases and the Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, Nebraska 68198-6805, USA.
Nowling
Tamara K
TK
Rizzino
Angie
A
D001665:Binding Sites; D015153:Blotting, Western; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000378:metabolism; D024002:HMGB Proteins; D006367:HeLa Cells; D006609:High Mobility Group Proteins / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D008954:Models, Biological; D016297:Mutagenesis, Site-Directed; D009687:Nuclear Proteins / Q000737:chemistry* / Q000378:metabolism; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D055748:SOXB1 Transcription Factors; D055751:SOXC Transcription Factors; D014157:Transcription Factors; D015533:Transcriptional Activation; D014162:Transfection
D004268:DNA-Binding Proteins; D024002:HMGB Proteins; D006609:High Mobility Group Proteins; D009687:Nuclear Proteins; C097473:SOX11 protein, human; C527782:SOX2 protein, human; D055748:SOXB1 Transcription Factors; D055751:SOXC Transcription Factors; D014157:Transcription Factors; D004247:DNA