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Crystal structure of the human FOXO3a-DBD/DNA complex suggests the effects of post-translational modification.

Tsai KL, Sun YJ, Huang CY, Yang JY, Hung MC, Hsiao CD - Nucleic Acids Res. (2007)

Bottom Line: Because these post-translational modification sites are located within the C-terminal basic region of the FOXO DNA-binding domain (FOXO-DBD), it is possible that these post-translational modifications could alter the DNA-binding characteristics.Based on a unique structural feature in the C-terminal region and results from biochemical and mutational studies, our studies may explain how FOXO-DBD C-terminal phosphorylation by protein kinase B (PKB) or acetylation by cAMP-response element binding protein (CBP) can attenuate the DNA-binding activity and thereby reduce transcriptional activity of FOXO proteins.In addition, we demonstrate that the methyl groups of specific thymine bases within the consensus sequence are important for FOXO3a-DBD recognition of the consensus binding site.

View Article: PubMed Central - PubMed

Affiliation: Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan.

ABSTRACT
FOXO3a is a transcription factor of the FOXO family. The FOXO proteins participate in multiple signaling pathways, and their transcriptional activity is regulated by several post-translational mechanisms, including phosphorylation, acetylation and ubiquitination. Because these post-translational modification sites are located within the C-terminal basic region of the FOXO DNA-binding domain (FOXO-DBD), it is possible that these post-translational modifications could alter the DNA-binding characteristics. To understand how FOXO mediate transcriptional activity, we report here the 2.7 A crystal structure of the DNA-binding domain of FOXO3a (FOXO3a-DBD) bound to a 13-bp DNA duplex containing a FOXO consensus binding sequence (GTAAACA). Based on a unique structural feature in the C-terminal region and results from biochemical and mutational studies, our studies may explain how FOXO-DBD C-terminal phosphorylation by protein kinase B (PKB) or acetylation by cAMP-response element binding protein (CBP) can attenuate the DNA-binding activity and thereby reduce transcriptional activity of FOXO proteins. In addition, we demonstrate that the methyl groups of specific thymine bases within the consensus sequence are important for FOXO3a-DBD recognition of the consensus binding site.

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Structural comparison of FOXO3a-DBD with other FOX/DNA complexes. Stereo diagram of superposition of the FOXO3a, FOXA2, FOXK1a and FOXP2/DNA complexes showing the Cα trace. For clarity, only the DNA in FOXO3a-DBD is shown, in light blue. FOXO3a, FOXA3, FOXK1a and FOXP2 are shown in red, yellow, green and blue, respectively.
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Figure 5: Structural comparison of FOXO3a-DBD with other FOX/DNA complexes. Stereo diagram of superposition of the FOXO3a, FOXA2, FOXK1a and FOXP2/DNA complexes showing the Cα trace. For clarity, only the DNA in FOXO3a-DBD is shown, in light blue. FOXO3a, FOXA3, FOXK1a and FOXP2 are shown in red, yellow, green and blue, respectively.

Mentions: A superimposition of the FOXO3a-DBD/DNA complex with the previously reported FOXA3, FOXK1a and FOXP2 DNA complexes showed a high degree of structural similarity in the core region (H1 ∼ H3 and S1 ∼ S3) with RMSDs of 0.64, 0.66 and 0.56 Å for Cα positions, respectively (Figure 5). However, there are several major structural deviations located in the H2–H3 turn, wing 1 and C-terminal regions, as the amino acid compositions and lengths of these regions are not well conserved. In the FOXA3 and FOXP2 complexes, both H2–H3 turns formed short α-helices. In contrast, the corresponding regions in FOXO3a and FOXK1a are coil structures. In particular, the H2–H3 turn region of FOXO3a has an insertion of five additional residues (198-GDSNS-202) that are solvent-exposed. The function of these extra residues is unknown, because there was no protein–DNA interaction in this region within the FOXO3a-DBD/DNA complex structure.Figure 5.


Crystal structure of the human FOXO3a-DBD/DNA complex suggests the effects of post-translational modification.

Tsai KL, Sun YJ, Huang CY, Yang JY, Hung MC, Hsiao CD - Nucleic Acids Res. (2007)

Structural comparison of FOXO3a-DBD with other FOX/DNA complexes. Stereo diagram of superposition of the FOXO3a, FOXA2, FOXK1a and FOXP2/DNA complexes showing the Cα trace. For clarity, only the DNA in FOXO3a-DBD is shown, in light blue. FOXO3a, FOXA3, FOXK1a and FOXP2 are shown in red, yellow, green and blue, respectively.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2175300&req=5

Figure 5: Structural comparison of FOXO3a-DBD with other FOX/DNA complexes. Stereo diagram of superposition of the FOXO3a, FOXA2, FOXK1a and FOXP2/DNA complexes showing the Cα trace. For clarity, only the DNA in FOXO3a-DBD is shown, in light blue. FOXO3a, FOXA3, FOXK1a and FOXP2 are shown in red, yellow, green and blue, respectively.
Mentions: A superimposition of the FOXO3a-DBD/DNA complex with the previously reported FOXA3, FOXK1a and FOXP2 DNA complexes showed a high degree of structural similarity in the core region (H1 ∼ H3 and S1 ∼ S3) with RMSDs of 0.64, 0.66 and 0.56 Å for Cα positions, respectively (Figure 5). However, there are several major structural deviations located in the H2–H3 turn, wing 1 and C-terminal regions, as the amino acid compositions and lengths of these regions are not well conserved. In the FOXA3 and FOXP2 complexes, both H2–H3 turns formed short α-helices. In contrast, the corresponding regions in FOXO3a and FOXK1a are coil structures. In particular, the H2–H3 turn region of FOXO3a has an insertion of five additional residues (198-GDSNS-202) that are solvent-exposed. The function of these extra residues is unknown, because there was no protein–DNA interaction in this region within the FOXO3a-DBD/DNA complex structure.Figure 5.

Bottom Line: Because these post-translational modification sites are located within the C-terminal basic region of the FOXO DNA-binding domain (FOXO-DBD), it is possible that these post-translational modifications could alter the DNA-binding characteristics.Based on a unique structural feature in the C-terminal region and results from biochemical and mutational studies, our studies may explain how FOXO-DBD C-terminal phosphorylation by protein kinase B (PKB) or acetylation by cAMP-response element binding protein (CBP) can attenuate the DNA-binding activity and thereby reduce transcriptional activity of FOXO proteins.In addition, we demonstrate that the methyl groups of specific thymine bases within the consensus sequence are important for FOXO3a-DBD recognition of the consensus binding site.

View Article: PubMed Central - PubMed

Affiliation: Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan.

ABSTRACT
FOXO3a is a transcription factor of the FOXO family. The FOXO proteins participate in multiple signaling pathways, and their transcriptional activity is regulated by several post-translational mechanisms, including phosphorylation, acetylation and ubiquitination. Because these post-translational modification sites are located within the C-terminal basic region of the FOXO DNA-binding domain (FOXO-DBD), it is possible that these post-translational modifications could alter the DNA-binding characteristics. To understand how FOXO mediate transcriptional activity, we report here the 2.7 A crystal structure of the DNA-binding domain of FOXO3a (FOXO3a-DBD) bound to a 13-bp DNA duplex containing a FOXO consensus binding sequence (GTAAACA). Based on a unique structural feature in the C-terminal region and results from biochemical and mutational studies, our studies may explain how FOXO-DBD C-terminal phosphorylation by protein kinase B (PKB) or acetylation by cAMP-response element binding protein (CBP) can attenuate the DNA-binding activity and thereby reduce transcriptional activity of FOXO proteins. In addition, we demonstrate that the methyl groups of specific thymine bases within the consensus sequence are important for FOXO3a-DBD recognition of the consensus binding site.

Show MeSH