Fig. 3. Effect of energy depletion on mRNP movement. (A to C) A transfected and transcriptionally induced cell, 10 min after energy depletion. (A) Concentrated YFP-MS2 nuclear mRNPs; (B) Hoechst DNA stain; (C) Merge of YFP-MS2 mRNPs from (A) in green and Hoechst from (B) in red, showing segregation into two domains [movies S12 to S14]. (D) Table summarizing the corral radius measured for corralled particles tracked at 37°C, 22°C, and ATP-depleted cells. %, percent of corralled particles from total tracked. (E to G) Cells treated with 0.02% Triton (pre, before Triton; 1, 7, and 15 s, after Triton). (E) Differential interference contrast image. (F) YFP-MS2 labeled mRNPs are lost from the nucleus during permeabilization (time in minutes). (G) Same as (F), but the cells were first energy depleted and then permeabilized, and mRNP loss is slower. (H) Plots of the mean fluorescence intensity over time in the nucleus of permeabilized cells, treated as in (F) (red and dark blue lines) or as in (G) (green and light blue lines). (I) Cell expressing H2B-YFP and (J) counterstained with Hoechst. (K) Merge of (I) and (J). (L to N) The same cell 10 min after ATP depletion, showing the formation of nuclear subdomains. Bar, 5 µm. [movies 15 to 17]. (O) Time course of a cell transfected with H2B-YFP in which squares have been photobleached to form a grid (times are in minutes). (P) Same time course as in O, but ATP was depleted at time 0 min, showing major changes in chromatin structure together with nuclear shrinkage [movie S18]. Bar, 5 µm.