Figure 6. KLP10A mediated MTs pole attachment models.

(A) Four possible KLP10A mediated MT pole attachment models based on the structures observed by EM (Figure 3). 1: Multiple pole-attached KLP10As depolymerize and keep the MT end attached to the pole. 2: Multiple KLP10As crosslink pole-unattached MTs to pole-attached ones. 3: Pole-unattached MTs interact with pole-attached ones through PFs with multiple KLP10As bound. 4: Ring of pole attached KLP10As and tubulin form a sleeve around a MT attaching it to the pole. All the MT-pole attachment models proposed could coexist together and analogous mechanisms could contribute to MT-kinetochore attachments. Structures resembling model 1 has been observed in the kinetochores of mammalian cells [54]. (B) Model to explain observed KLP10A KT2M rescue phenotype of S2 cells. Top: In control and WT-rescue rescue cells the MTs comprising each kinetochore fiber (K-fiber) are tightly bundled and attached to poles and kinetochores. Bottom: In KT2M-rescue cells the altered Kin-Tub-2 binding site of KLP10A results in the detachment and separation of MTs from the K-fiber bundles. Random uneven loss of MTs from sister K-fibers results in kinetochore misalignments. The MTs separated from poles and kinetochores lead to the appearance of a larger and less organized spindle. Red/pink spheres: KLP10AHD; Red strings: KLP10A N and C terminal tails; Ochre cylinders and lines: MTs, Orange blob: MT capping proteins; Gray circles: spindle pole matrix in gray; Black ellipses: kinetochores.