Structural basis for DNA recognition by FoxO1 and its regulation by posttranslational modification - PubMed (original) (raw)

Structural basis for DNA recognition by FoxO1 and its regulation by posttranslational modification

Michael M Brent et al. Structure. 2008.

Abstract

FoxO transcription factors regulate the transcription of genes that control metabolism, cellular proliferation, stress tolerance, and possibly life span. A number of posttranslational modifications within the forkhead DNA-binding domain regulate FoxO-mediated transcription. We describe the crystal structures of FoxO1 bound to three different DNA elements and measure the change in FoxO1-DNA affinity with acetylation and phosphorylation. The structures reveal additional contacts and increased DNA distortion for the highest affinity DNA site. The flexible wing 2 region of the forkhead domain was not observed in the structures but is necessary for DNA binding, and we show that p300 acetylation in wing 2 reduces DNA affinity. We also show that MST1 phosphorylation of FoxO1 prevents high-affinity DNA binding. The observation that FoxO-DNA affinity varies between response elements and with posttranslational modifications suggests that modulation of FoxO-DNA affinity is an important component of FoxO regulation in health and misregulation in disease.

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Figures

Figure 1

Figure 1

FoxO1 secondary structure and sequence alignment of human FoxO1 DBD with other forkhead domains. Residues that undergo phosphorylation or acetylation are marked with a red circle or a blue triangle respectively.

Figure 2

Figure 2

Structures of FoxO1/DNA complexes (a) Representative FoxO1 DBD/DNA complex - 2.1 Å structure of FoxO1 bound to the DBE1 sequence. The eight base DBE sequence is in CDK coloring and flanking bases are gray. (b and c) Stereo view of helix 3 interactions with DNA showing the different interactions with IRE (b) and DBE (c) DNA mediated by Asn211 and His215. Electron density shown is from a simulated annealing omit map contoured at 1.0 σ around the DNA recognition helix. (d) Superposition of FoxO1 DBD bound to DBE1 and DBE2 DNAs to illustrate the larger amount of bend in the DNA for the DBE2 structure. FoxO1 DBD bound to DBE1 is colored in blue and gray. FoxO1 DBD bound to DBE2 is colored in tan and red. (e–g) The targets of MST1 phosphorylation and their interactions with the phosphate backbone of DNA. Structure shown is FoxO1 DBD/DBE1 DNA. The interactions are conserved in the FoxO1/IRE DNA structure. (e) Ser212. (f) Ser218. (g) Ser234 and Ser235.

Figure 3

Figure 3

Schematic showing FoxO1 DBD interactions with IRE (a) and DBE1 (b) DNA sequences. Differences in hydrogen bonding between the DBE and IRE sequences are highlighted in green. Bases that are contacted directly or through water mediated interactions are shaded. Phosphates that are contacted directly or through water mediated interactions are highlighted in red.

Figure 4

Figure 4

(a–d) Measurement of binding affinity to IRE and DBE2 DNA for C-terminally truncated FoxO1 DBD constructs.

Figure 5

Figure 5

(a) EMSA results showing the difference in affinity for FoxO1 151–266 binding to IRE, DBE2 and DBE1 DNA sequences. (b–e) EMSA results showing the effects of FoxO1 151–266 modifications on binding affinity for IRE and DBE2 DNA sequences.

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