Figure 5: CSD interactions accelerate HP1 association dynamics.
From: Multivalency governs HP1α association dynamics with the silent chromatin state
(a) Confocal flurescence images of NIH 3T3 cells transfected with mEos3.2-HP1a, mEos3.2-HP1α(I163E) or mEos3.2-HP1α(W174A) and overlay with Hoechst staining. Scale bar, 5 μm. (b) Time series of images from a typical FRAP experiment (HP1α), showing the bleached spot as a red circle pre- and post bleach at indicated times. Scale bar, 5 μm. (c) FRAP analysis of mEos3.2-HP1α wt or W174A in heterochromatin foci (n=15 cells with two foci from each, the shaded area denotes the standard deviation at each time point). Analysis of the traces using a diffusion/binding model46 results in the following values: HP1α: λon=1.2±0.4 s and τoff=2.8±1.2 s, HP1α(W174A): λon=1.0±0.2 s and τoff=1.1±0.3 s, HP1α(I163E): λon=1.8±0.3 s and τoff=0.8±0.1 s. (c) Comparison of the average dissociation time constants τoff,1 and τoff,2 (fast and slow phase) between HP1α in the absence and presence of P3 (error bars: s.e.m., n=4–16 replicates, *P<0.05, Student’s t-test). (d) Comparison of the average dissociation time constants τoff,1 and τoff,2 (fast and slow phase) between HP1α in the absence and presence of P3 (error bars: s.e.m., n=4–16 replicates, *P<0.05, Student’s t-test). (e) Comparison of the association rate constant kon between HP1α in the absence and presence of P3 (errors: s.e.m., n=4–16 replicates, *P<0.05, Student’s t-test). (c,d) For all fit results, see Table 1.
