In simulations, tension-dependent kMT dynamics can explain tension regulation. (A) kMT dynamics in the simulation are governed by: (1) kMT dynamic instability with constant growth (v_g) and shortening (v_s) rates and with basal catastrophe (k_C,0) and rescue (k_R,0) frequencies; (2) kMT catastrophe frequency that increases with kMT length; and (3) kMT rescue frequency that increases with pericentromere tension. (B–E) Comparison of experimental images to simulated images convolved from the model (red, Spc110-mCherry; green, Nuf2-GFP). Bars, 1 µm. Exp = experimental image; Sim = simulated image; NC = no change. (B) WT experimental results compared with WT simulations. (C) top2-4 experimental results compared with simulations using longer top2-4 experimental spindle lengths with WT pericentromere stiffness. (D) top2-4 experimental results compared with simulations using reduced pericentromere stiffness and WT experimental spindle lengths. (E) top2-4 experimental results compared with simulations using reduced pericentromere stiffness and longer top2-4 experimental spindle lengths. (F) Pericentromere tension is regulated by spindle structure: increased stretch of the softer top2-4 pericentromere (light gray spring) relative to a stiffer WT pericentromere (dark gray) leads to similar tension (F_tension) because of increased spindle lengths and reduced kMT lengths. Error bars = SEMs.