Persistent presence of Mps1 maintains Mad1 and Mad2 on attached, bioriented kinetochores. (A and B) Mad2 localization at kinetochores of U2OS cells transiently transfected with LAP-Mps1-WT or LAP-Mis12-Mps1-WT, treated as indicated. Graph shows distribution of cells with high, low/medium, or no Mad2 signal on kinetochores. (C) Close-up of Mad2 localization at individual kinetochore pairs of U2OS cells treated and transfected as in A. (D) Mad2 intensity related to interkinetochore distance of kinetochore pairs in cells transfected and treated as in A.