Figure 7.

“Dog leash” model of CPC function. (A) The idea behind the “dog leash” model is that the localization module of the CPC (the owner) is tethered at the base of kinetochores. INCENP acts as a “dog leash” that allows the “dog,” Aurora B, to phosphorylate substrates only within limits defined by the length of the linker (which may vary, e.g., as a consequence of phosphorylation). This defines a boundary between regions where the dog is allowed and regions where it is not. (B,C) Application of the dog leash model to kinetochores. Under low tension (B), Aurora B can reach out in the kinetochore and phosphorylate substrates there. Under high tension (C), substrates (e.g., in the KMN network) have crossed the boundary defined by the leash and become unreachable. Note that in this drawing the CPC is tethered at the base of the kinetochore and its position is stationary, but this may not be the case and tension might increase its distance from the CENP-A base of the kinetochore. The function of a phosphatase is implicit in the model.