PBX1 and MEIS1 up-regulate SOX3 gene expression by direct interaction with a consensus binding site within the basal promoter region.
Sox3/SOX3 [SRY (sex determining region Y)-box 3] is considered to be one of the earliest neural markers in vertebrates, playing a role in specifying neuronal fate. We have previously reported characterization of the SOX3 promoter and demonstrated that the general transcription factors NF-Y (nuclear factor-Y), Sp1 (specificity protein 1) and USF (upstream stimulatory factor) are involved in transcriptional regulation of SOX3 promoter activity. In the present study we provide the first evidence that the TALE (three-amino-acid loop extension) transcription factors PBX1 (pre-B-cell leukaemia homeobox 1) and MEIS1 (myeloid ecotropic viral integration site 1 homologue) participate in regulating human SOX3 gene expression in NT2/D1 cells by direct interaction with the consensus PBX/MEIS-binding site, which is conserved in all mammalian orthologue promoters analysed. PBX1 is present in the protein complex formed at this site with nuclear proteins from uninduced cells, whereas both PBX1 and MEIS1 proteins were detected in the complex created with extract from RA (retinoic acid)-induced NT2/D1 cells. By functional analysis we also showed that mutations of the PBX1/MEIS1-binding sites resulted in profound reduction of SOX3 promoter responsiveness to RA. Finally, we demonstrated that overexpressed PBX1 and MEIS1 increased endogenous SOX3 protein expression in both uninduced and RA-induced NT2/D1 cells. With the results of the present study, for the first time, we have established a functional link between the TALE proteins, PBX1 and MEIS1, and expression of the human SOX3 gene. This link is of particular interest since both TALE family members and members of the SOX superfamily are recognized as important developmental regulators.
Institute of Molecular Genetics and Genetic Engineering, University of Belgrade, Vojvode Stepe 444a, PO Box 23, 11010 Belgrade, Serbia.
Marija
M
Mojsin
Milena
M
Stevanovic
D000970:Antineoplastic Agents / Q000494:pharmacology; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D015153:Blotting, Western; D045744:Cell Line, Tumor; D016384:Consensus Sequence; D018983:DNA Footprinting; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D003850:Deoxyribonuclease I / Q000378:metabolism; D024202:Electrophoretic Mobility Shift Assay; D005786:Gene Expression Regulation; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D000075064:Myeloid Ecotropic Viral Integration Site 1 Protein; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D000075062:Pre-B-Cell Leukemia Transcription Factor 1; D011401:Promoter Regions, Genetic / Q000235:genetics*; D011485:Protein Binding; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D055748:SOXB1 Transcription Factors / Q000235:genetics*; D012689:Sequence Homology, Nucleic Acid; D014212:Tretinoin / Q000494:pharmacology; D015854:Up-Regulation / Q000187:drug effects
D000970:Antineoplastic Agents; D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; C000616391:MEIS1 protein, human; D000075064:Myeloid Ecotropic Viral Integration Site 1 Protein; D009363:Neoplasm Proteins; D000075062:Pre-B-Cell Leukemia Transcription Factor 1; D011518:Proto-Oncogene Proteins; C527785:SOX3 protein, human; D055748:SOXB1 Transcription Factors; C083400:PBX1 protein, human; D014212:Tretinoin; D003850:Deoxyribonuclease I