DDB2 immobilization elicits extensive chromatin unfolding. (A–F) AO3 cells containing a 90-Mbp heterochromatic array were transfected with mCherry-LacR (A), mCherry-LacR-DDB2 in the absence (B) or presence (C) of HAT inhibitor (HATi), mCherry-LacR-DDB2^K244E (D), mCherry-LacR-DDB2^D307Y (E), or mCherry-LacR-DDB2^L350P (F). Images show a confocal slice (1 Airy unit) of the nuclear distribution of the mCherry-LacR fusion proteins. The lookup table for the color coding is shown left of A and D. (G) Quantification of the relative array size (surface of the array/surface of the nucleus) is shown in a box plot (50–100 cells for each condition). Open circles are data points that are considered outliers, as their value is greater than the upper quartile, +1.5 the interquartile distance, or less than the lower quartile, −1.5 the interquartile distance. (H) Mouse NIH2/4 cells containing a 256x LacO array were transfected with mCherry-LacR (left) or mCherry-LacR-DDB2 (right). (I) Human U2OS 2–6-3 cells containing 200 copies of a LacO-containing cassette (∼4 Mbp) were transfected with mCherry-LacR (left) or mCherry-LacR-DDB2 (right).