Spatially precise DNA bending is an essential activity of the sox2 transcription factor.
Sox proteins, a subclass of high mobility group box proteins, govern cell fate decisions by acting both as classical transcription factors and architectural components of chromatin. We aimed to demonstrate that the DNA bending activity of Sox proteins is essential to regulate gene expression. We focused on mouse Sox2, which participates in the transactivation of the Fgf4 (fibroblast growth factor 4) gene in the inner cell mass of the blastocyst. We generated six substitutions in the high mobility group box of Sox2. One mutant showed a reduced DNA bending activity on the Fgf4 enhancer (46 degrees instead of 80 degrees), which resulted in more powerful transactivation compared with the wild type protein. We then selected two single-base mutations in the Fgf4 enhancer that make the DNA less bendable by the Sox2 protein. Again, a different DNA bend (0 degrees and 42 degrees instead of 80 degrees) resulted in a different activation of transcription, but in this case reduced bending corresponded to decreased transcription. We found that the opposite effect on transcription of similar DNA bending angles is due to a 20 degrees difference in the relative orientation of the DNA bends, proving that a correct three-dimensional geometry of enhanceosome complexes is necessary to promote transcription.
Scaffidi
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San Raffaele Scientific Institute, via Olgettina 58, 20132 Milan, Italy.
Bianchi
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D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D001755:Blastocyst / Q000378:metabolism; D002843:Chromatin / Q000378:metabolism; D004247:DNA / Q000737:chemistry* / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004742:Enhancer Elements, Genetic; D005346:Fibroblast Growth Factors / Q000096:biosynthesis / Q000235:genetics; D015870:Gene Expression; D005822:Genetic Vectors; D005982:Glutathione Transferase / Q000378:metabolism; D024002:HMGB Proteins; D007700:Kinetics; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D009687:Nuclear Proteins / Q000378:metabolism*; D009690:Nucleic Acid Conformation; D050814:Octamer Transcription Factor-3; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D055748:SOXB1 Transcription Factors; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014162:Transfection
D002843:Chromatin; D004268:DNA-Binding Proteins; D024002:HMGB Proteins; D009687:Nuclear Proteins; D050814:Octamer Transcription Factor-3; C494174:Pou5f1 protein, mouse; D055748:SOXB1 Transcription Factors; C527783:Sox2 protein, mouse; D014157:Transcription Factors; C112971:fibroblast growth factor 14; D005346:Fibroblast Growth Factors; D004247:DNA; D005982:Glutathione Transferase