Figure 3

Fluorescence correlation spectroscopy reveals changes on Oct4 and Sox2 interactions with chromatin at the onset of differentiation. Single-point FCS measurements were run in undifferentiated Oct4-YPet and Sox2-YPet ES cells (light colors) or 48 h after LIF/2i withdrawal (early-differentiated, dark colors). (a,b) Mean, normalized ACF obtained at the nucleoplasm (top panel) and foci (bottom panel). (c,d) The ACF data were fitted with Eq. 1 to obtain the fractions of free, long-lived bound and short-lived bound TFs and the characteristic times of long-lived and short-lived interactions of the TFs with chromatin. Experimental results were expressed as mean ± SEM (FCS experiments in the nucleoplasm: n_{data Oct4} = 54 and 73 and n_{data Sox2} = 110 and 146 for the undifferentiated and early-differentiated conditions, respectively; FCS experiments at foci: n_{data Oct4} = 15 and 19 and n_{data Sox2} = 20 and 14 for the undifferentiated and early-differentiated conditions, respectively). We only run a single experiment in each cell to minimize its photodamage. Asterisks (*) indicate significant differences (p < 0.01) between undifferentiated and early-differentiated ES cells.