Journal: eLife
Article Title: Optogenetic control of PRC1 reveals its role in chromosome alignment on the spindle by overlap length-dependent forces
doi: 10.7554/eLife.61170
Figure Lengend Snippet: ( A ) Spindle (first block, left) in a U2OS cell with stable expression of CENP-A-GFP (not shown), immunostained for endogenous Kif4A (AF-594, green), PRC1 (AF-647, magenta) and stained with DAPI (cyan). Enlargements of the boxed region are shown (right). White arrowhead points to Kif4A outside chromosomes, at the position where PRC1-AF-647 is found, which corresponds to the bridging fiber. Spindle (middle block, top) in a U2OS cell with stable expression of CENP-A-GFP (cyan), immunostained for endogenous Kif18A (AF-594, green) and PRC1 (AF-647, magenta). Enlargements of the boxed region are shown (bottom). White arrowhead points to Kif18A in the bridging fiber where PRC1-AF-647 is found. Spindle (right block, top) of HeLa cell stably expressing MKLP1-GFP (green) and stained for SiR-tubulin (magenta). Enlargements of the boxed region are shown (bottom). White arrowhead points to the MKLP1 in the bridging fiber. Schemes (right) show Kif4A and Kif18A localization on chromosome arms and plus ends of k-fibers, respectively, and Kif4A, Kif18A, and MKLP1 in the bridging fiber. ( B ) Time-lapse images (left block) of unlabeled U2OS cell with transient expression of opto-PRC1 (magenta), iLID-CAAX and GFP-Kif4A (green), and stained with SiR-DNA (cyan) before (Dark, top) and after 12 min of the exposure to the blue light (Light, middle). Enlargements of the boxed regions are shown (bottom rows). Before opto-PRC1 removal (Dark) Kif4A is also found outside chromosomes, at the position of opto-PRC1 labeled bundles (white arrowheads). Note that after 12 min of opto-PRC1 removal (Light), Kif4A signal is found only at the positions of the chromosomes. The intensities in the enlargements are adjusted differently than those of the whole spindle to better point out localization of proteins. Time-lapse images (right block) of unlabeled U2OS cell with transient expression of opto-PRC1 (magenta), iLID-CAAX and EGFP-Kif18A (green) before (Dark, top) and after 12 min of the exposure to the blue light (Light, middle). Enlargements of the boxed regions are shown (bottom). Before opto-PRC1 removal (Dark, bottom left) Kif18A is found in the bridging fiber (white arrowhead). In the enlargement of the boxed region after 12 min of opto-PRC1 removal (Light, bottom right), the signal of the EGFP-Kif18A on the bridging fiber is weaker. ( C ) Normalized bridging fiber Kif4A (left) and Kif18A (right) intensity measured before and after acute and long-term PRC1 removal in cells as in B and A, respectively. Dark; black, Light; cyan, untreated; magenta, PRC1 siRNA; green. ( D ) Timelapse of the spindle in HeLa BAC cell (left) stably expressing MKLP1-GFP (gray) with transient expression of opto-PRC1 (not shown) and iLID-CAAX, and stained with SiR-DNA (not shown) before (0 min, Dark), at the end of continuous exposure (20 min, Light) and 10 min after cessation of exposure to the blue light (30 min, Dark). Note that opto-PRC1 is not shown in order to point out localization of MKLP1-GFP. Image is a maximum projection of three z-planes. Graph (right) shows normalized bridging fiber MKLP1 intensity measured before and after acute and long-term PRC1 removal in cells as in . ( E ) Spindles from HeLa cells stably expressing PRC1-GFP (gray) in untreated (left), Kif4A siRNA (middle), and Kif18A siRNA (right) -treated cell. ( F ) Ratios of overlap and spindle lengths for untreated (black), Kif4A siRNA (magenta), and Kif18A siRNA (green) -treated cells. Gray scattered points show individual measurements. ( G ) Difference in PRC1-labeled overlap and spindle length for Kif4A siRNA (magenta) and Kif18A siRNA (green) treatment when compared to untreated cells. Numbers in brackets; number of measurements and cells, respectively. Statistical analysis: t-test ( C, G ); one-way ANOVA ( F ). All images are smoothed with 0.5-pixel-sigma Gaussian blur, and one z-plane is shown unless stated otherwise. Scale bars: 2 µm.
Article Snippet: Following primary antibodies were used: mouse anti-PRC1 monoclonal antibody (1:100; C-1; sc-376983, Santa Cruz Biotechnology), rabbit anti-α-tubulin polyclonal antibody (1:100; RRID: AB_10743646 ; SAB4500087; Sigma-Aldrich Corporation, St. Louis, MO, USA), mouse monoclonal anti-Kif4A antibody (1:100; RRID: AB_10707683 ; E-8; sc-365144; Santa Cruz Biotechnology), rabbit polyclonal anti-MKLP1 antibody (1:100; RRID: AB_631959 ; N-19; sc-867, Santa Cruz Biotechnology), mouse monoclonal anti-Eg5 antibody (1:100; RRID: AB_10841907 ; A-1; sc-365681, Santa Cruz Biotechnology), rabbit polyclonal anti-Kif18A antibody (1:100; RRID: AB_2296551 ; A301-080A; Bethyl), rabbit polyclonal anti-Kif4A antibody (1:200; RRID: AB_2280904 ; A301-074A; Bethyl).
Techniques: Blocking Assay, Expressing, Staining, Stable Transfection, Labeling