Fukuda Yusuke, Luchniak Anna, Murphy Erin R, Gupta Mohan L
Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637, USA.
Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL 60637, USA.
Curr Biol. 2014 Aug 18;24(16):1826-35. doi: 10.1016/j.cub.2014.06.069. Epub 2014 Jul 31.
To function in diverse cellular processes, the dynamic behavior of microtubules (MTs) must be differentially regulated within the cell. In budding yeast, the spindle position checkpoint (SPOC) inhibits mitotic exit in response to mispositioned spindles. To maintain SPOC-mediated anaphase arrest, astral MTs must maintain persistent interactions with and/or extend through the bud neck. However, the molecular mechanisms that ensure the stability of these interactions are not known.
The presence of an MT extending through and/or interacting with the bud neck is maintained by spatial control of catastrophe and rescue, which extends MT lifetime >25-fold and controls the length of dynamic MTs within the bud compartment. Moreover, the single kinesin-8 motor Kip3 alternately mediates both catastrophe and rescue of the bud MT. Kip3 accumulates in a length-dependent manner along the lattice of MTs within the bud, yet induces catastrophe spatially near the bud tip. Rather, this accumulation of Kip3 facilitates its association with depolymerizing MT plus ends, where Kip3 promotes rescue before MTs exit the bud. MT rescue within the bud requires the tail domain of Kip3, whereas the motor domain mediates catastrophe at the bud tip. In vitro, Kip3 exerts both stabilizing and destabilizing effects on reconstituted yeast MTs.
The kinesin-8 Kip3 is a multifunctional regulator that differentially stabilizes and destabilizes specific MTs. Control over MT catastrophe and rescue by Kip3 defines the length and lifetime of MTs within the bud compartment of cells with mispositioned spindles. This subcellular regulation of MT dynamics is critical to maintaining mitotic arrest in response to mispositioned spindles.
为了在多种细胞过程中发挥作用，微管（MTs）的动态行为必须在细胞内受到差异调节。在芽殖酵母中，纺锤体位置检查点（SPOC）会响应纺锤体位置错误而抑制有丝分裂退出。为了维持SPOC介导的后期停滞，星状微管必须与芽颈保持持续相互作用和/或延伸穿过芽颈。然而，确保这些相互作用稳定性的分子机制尚不清楚。
通过对微管灾变和营救的空间控制，维持了延伸穿过芽颈和/或与芽颈相互作用的微管的存在，这使微管寿命延长了25倍以上，并控制了芽区室内动态微管的长度。此外，单驱动蛋白-8马达Kip3交替介导芽微管的灾变和营救。Kip3沿着芽内微管的晶格以长度依赖的方式积累，但在芽尖附近在空间上诱导灾变。相反，Kip3的这种积累促进了它与解聚的微管正端的结合，在微管离开芽之前，Kip3在那里促进营救。芽内的微管营救需要Kip3的尾部结构域，而马达结构域在芽尖介导灾变。在体外，Kip3对重组酵母微管既有稳定作用又有去稳定作用。
驱动蛋白-8 Kip3是一种多功能调节因子，它对特定微管有差异地稳定和去稳定作用。Kip3对微管灾变和营救的控制决定了纺锤体位置错误的细胞芽区内微管的长度和寿命。这种微管动力学的亚细胞调节对于响应纺锤体位置错误维持有丝分裂停滞至关重要。
