Fig. 9. Actinomycin D treatment led to chromosome end-to-end fusions in mitotic cells. In response to actinomycin D treatment some telophase MCF-7 cells displayed chromosome end-to-end fusions (A) as well as the presence of TRF2 at the junctions of the observed chromosomal arcs (B). B' represents the magnified area framed in B. Chromosome fusion from cells undergoing cytokinesis is also shown (C-E). Co-localization of TRF2 with the telomere-binding protein Tin2 is shown in untreated (F-I) and actinomycin D-treated (J-M) MCF-7 cells. H', H'' and L' present profiles of fluorescence measurements along the indicated red lines shown in the same panel. Large arrows (F-M) indicate nucleoli and small arrows chromosome fusions (A-E) or telomeres (F-I and J-M). Total amounts of TRF2 were determined by western blotting of lysates of untreated and actinomycin D-treated MCF-7 cells (N). The lysates were prepared by directly dissolving cells on culture dishes into equal volumes of SDS-PAGE loading buffer.