Figure 1.

Sox2 cooperatively binds to the NANOG upstream promoter (DNA^NANOG). (a) DNA binding of Sox2^HMG was probed by monitoring changes in fluorescence anisotropy of Alexa Fluor 647-labeled dsDNA with increasing [Sox2^HMG]. The solid line represents nonlinear least squares (NLS) fit of the data to a Hill equation. NLS-derived parameters: K_D = 15.1 (±2.0) nM, Hill coefficient = 1.5 (±0.3). (b) Fluorescence electrophoretic mobility assay (fEMSA) of Sox2^HMG-DNA^NANOG binding suggests a multistep Sox2^HMG complex formation with dsDNA^NANOG involving multiple protein molecules that are able to bind the DNA partner. (See also Figure S2.)