Recognition mechanism of Wilms' tumour suppressor protein and DNA triplets: insights from molecular dynamics simulation and free energy analysis.

The Wilms' tumour suppressor protein (WT1) plays a multifaceted role in human cancer processes. Mutations on its DNA recognition domain could lead to Denys-Drash syndrome, and alternate splicing results in insertion of the tripeptide Lys-Thr-Ser (KTS) between the third and fourth zinc fingers (ZFs), leading to changes in the DNA-binding function. However, detailed recognition mechanisms of the WT1-DNA complex have not been explored. To clarify the mutational effects upon WT1 towards DNA binding at the atomic level, molecular dynamics simulations and the molecular mechanics/Poisson Boltzmann surface area (MM/PBSA) method were employed. The simulation results indicate that mutations in ZF domains (E427Q and Q369H) may weaken the binding affinity, and the statistical analyses of the hydrogen bonds and hydrophobic interactions show that eight residues (Lys351, Arg366, Arg375, Arg376, Lys399, Arg403, Arg424 and Arg430) have a significant influence on recognition and binding to DNA. Insertion of the tripeptide KTS could form an immobilized hydrogen-bonding network with Arg403, affecting the flexibility and angle of the linker between ZF3 and ZF4, thus influencing the recognition between the protein and the DNA triplet at its 5' terminus. These results represent the first step towards a thorough characterization of the WT1 recognition mechanisms, providing a better understanding of the structure-function relationship of WT1 and its mutants.