Figure 2.

Two mobile populations of HP1 proteins in euchromatin. (A) LSM image of a HEp-2 cell stably expressing GFP-HP1α before FCS measurement. The cross indicates the position were the corresponding FCS measurement was performed. (B) Count rate trace of the FCS measurement shown in A. Pronounced spikes corresponding to large brightly stained HP1-containing structures with low mobility are indicated by arrows. (C) Count rate trace of FCS measured at the same position after a 5-s bleach pulse of the confocal volume. (D) Autocorrelation curves after amplitude normalization of GFP-HP1α (blue line), GFP-HP1β (red line), GFP-HP1γ (green line), GFP-HP1γC59R (gray line), and GFP alone (black dotted line) measured in euchromatic regions of the nucleus. (E) Fitting of the measured autocorrelation curve of HP1α (black line) with an anomalous diffusion model (red dotted line). (F) Diffusion coefficients of GFP proteins as determined by FCS in the nucleus and in the cytoplasm (cyto).