Forkhead Domains of FOXO Transcription Factors Differ in both Overall Conformation and Dynamics.

Katarina Psenakova,Klara Kohoutova,Vaclav Veverka,Tomas Obsil,Michael Ausserlechner,Veronika Obsilova

doi:10.3390/cells8090966

Katarina Psenakova, Klara Kohoutova + Show 4 more

Open Access

https://doi.org/10.3390/cells8090966

Copy DOI

Abstract

FOXO transcription factors regulate cellular homeostasis, longevity and response to stress. FOXO1 (also known as FKHR) is a key regulator of hepatic glucose production and lipid metabolism, and its specific inhibition may have beneficial effects on diabetic hyperglycemia by reducing hepatic glucose production. Moreover, all FOXO proteins are considered potential drug targets for drug resistance prevention in cancer therapy. However, the development of specific FOXO inhibitors requires a detailed understanding of structural differences between individual FOXO DNA-binding domains. The high-resolution structure of the DNA-binding domain of FOXO1 reported in this study and its comparison with structures of other FOXO proteins revealed differences in both their conformation and flexibility. These differences are encoded by variations in protein sequences and account for the distinct functions of FOXO proteins. In particular, the positions of the helices H1, H2 and H3, whose interface form the hydrophobic core of the Forkhead domain, and the interactions between hydrophobic residues located on the interface between the N-terminal segment, the H2-H3 loop, and the recognition helix H3 differ among apo FOXO1, FOXO3 and FOXO4 proteins. Therefore, the availability of apo structures of DNA-binding domains of all three major FOXO proteins will support the development of FOXO-type-specific inhibitors.

Highlights

The members of the Forkhead box (FOX) family of transcription factors share a conserved winged-helix DNA-binding domain (DBD) known as the Forkhead domain [1,2]
Structures, the region between helices H2 and H3 of FOXO1-DBD contains an additional short helix, H4, which partly overlaps with the N-terminal end of the 5-amino-acid insertion [45,46]
The results suggested that FOXO1-DBD is more compact than the other two FOXO proteins, whereas FOXO4-DBD appears to be less compact, based on the sum of Cα -Cα distances between selected Ile residues

Summary

Introduction

The members of the Forkhead box (FOX) family of transcription factors share a conserved winged-helix DNA-binding domain (DBD) known as the Forkhead domain [1,2]. This domain consists of approximately 110 amino acids and folds into three major α-helices (H1-H3), a short twisted three-stranded antiparallel β-sheet (comprising three β strands S1–S3) and two wing-like loops W2), and their arrangement within the Forkhead domain is H1-S1-H2-H3-S2-W1-S3-W2 [3]. The DNA-binding surface includes the loop region W1, the loop between helices H4 and H3 and the N-terminal segment preceding the helix H1. Forkhead domains of FOXO proteins contain a 5-amino-acid insertion between α-helices H2 and. All FOXO-DBDs recognize consensus sequences 50 -GTAAACAAtab-30 and

Methods

Results

Conclusion