title: A thermodynamic basis of DNA sequence selectivity by the ETS domain of murine PU.1.
abstract: The ETS domain of the transcription factor PU.1 tolerates a large number of DNA cognate variants that differ exclusively in the sequences flanking a critical central consensus, 5'-GGAA-3'. We investigated the thermodynamics of site selection by the DNA-binding domain by following the PU.1 ETS/DNA equilibrium with a large set of cognate variants under various temperature and salt conditions by filter binding. Our results indicate that the stability of the ETS/DNA complex is quantitatively tied to variations in the change in heat capacity. Thermodynamic effects induced by changing Na(+) concentrations from 150 mM to 250 mM are complex and not readily interpreted by polyelectrolyte theory. We also extended our understanding of data from our previous investigation on energetic base-neighbour coupling, by dissecting the thermodynamic contributions underlying the observed free-energy coupling. In conjunction with available structural and biochemical data, we propose that site selectivity by the PU.1 ETS domain arises from differential protein/DNA contacts in the flanking sequences that modulate the orientation of the ETS recognition helix and trigger a coupled reduction in the flexibility observed in the unbound ETS domain.
authors.affiliation: Department of Pharmaceutical Sciences, University of Toronto, 19 Russell Street, M5S 2S2, Toronto, Ont., Canada.
authors.forename: Gregory M K
authors.initials: GM
authors.lastname: Poon
authors.forename: Robert B
authors.initials: RB
authors.lastname: Macgregor
mesh_terms: D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D004247:DNA / Q000737:chemistry* / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism; D051379:Mice; D009994:Osmolar Concentration; D018583:Pliability; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011518:Proto-Oncogene Proteins / Q000737:chemistry* / Q000378:metabolism; D050783:Proto-Oncogene Proteins c-ets; D012964:Sodium / Q000494:pharmacology; D013696:Temperature; D013816:Thermodynamics; D015534:Trans-Activators / Q000737:chemistry* / Q000378:metabolism; D014157:Transcription Factors / Q000737:chemistry; D000099232:Proto-Oncogene Protein Spi-1
chemical_list: D004247:DNA; D004268:DNA-Binding Proteins; D011518:Proto-Oncogene Proteins; D050783:Proto-Oncogene Proteins c-ets; D012964:Sodium; D015534:Trans-Activators; D014157:Transcription Factors; D000099232:Proto-Oncogene Protein Spi-1