title: Distinct Roles for Interfacial Hydration in Site-Specific DNA Recognition by ETS-Family Transcription Factors.
abstract: The ETS family of transcription factors is a functionally heterogeneous group of gene regulators that share a structurally conserved, eponymous DNA-binding domain. Unlike other ETS homologues, such as Ets-1, DNA recognition by PU.1 is highly sensitive to its osmotic environment due to excess interfacial hydration in the complex. To investigate interfacial hydration in the two homologues, we mutated a conserved tyrosine residue, which is exclusively engaged in coordinating a well-defined water contact between the protein and DNA among ETS proteins, to phenylalanine. The loss of this water-mediated contact blunted the osmotic sensitivity of PU.1/DNA binding, but did not alter binding under normo-osmotic conditions, suggesting that PU.1 has evolved to maximize osmotic sensitivity. The homologous mutation in Ets-1, which was minimally sensitive to osmotic stress due to a sparsely hydrated interface, reduced DNA-binding affinity at normal osmolality but the complex became stabilized by osmotic stress. Molecular dynamics simulations of wildtype and mutant PU.1 and Ets-1 in their free and DNA-bound states, which recapitulated experimental features of the proteins, showed that abrogation of this tyrosine-mediated water contact perturbed the Ets-1/DNA complex not through disruption of interfacial hydration, but by inhibiting local dynamics induced specifically in the bound state. Thus, a configurationally identical water-mediated contact plays mechanistically distinct roles in mediating DNA recognition by structurally homologous ETS transcription factors.
authors.affiliation: Department of Chemistry, Georgia State University , Atlanta, Georgia 30303, United States.
authors.forename: Suela
authors.initials: S
authors.lastname: Xhani
authors.affiliation: Department of Chemistry, Georgia State University , Atlanta, Georgia 30303, United States.
authors.forename: Shingo
authors.initials: S
authors.lastname: Esaki
authors.affiliation: Department of Chemistry, Georgia State University , Atlanta, Georgia 30303, United States.
authors.forename: Kenneth
authors.initials: K
authors.lastname: Huang
authors.affiliation: Department of Chemistry, Georgia State University , Atlanta, Georgia 30303, United States.
authors.forename: Noa
authors.identifier: 0000-0002-4126-522X
authors.initials: N
authors.lastname: Erlitzki
authors.affiliation: Department of Chemistry, Georgia State University , Atlanta, Georgia 30303, United States.|Center for Diagnostics and Therapeutics, Georgia State University , Atlanta, Georgia 30303, United States.
authors.forename: Gregory M K
authors.identifier: 0000-0001-5107-9458
authors.initials: GM
authors.lastname: Poon
mesh_terms: D004247:DNA / Q000737:chemistry*; D006801:Humans; D056004:Molecular Dynamics Simulation; D050783:Proto-Oncogene Proteins c-ets / Q000737:chemistry*; D014867:Water / Q000737:chemistry
chemical_list: D050783:Proto-Oncogene Proteins c-ets; D014867:Water; D004247:DNA