Molecular Delineation Of Mps1-Aurora B Signaling Cascade In Mitosis

During cell division, a successful cell division is equal distribution of the genetic material into two daughter cells. The interactions between the kinetochore and spindle microtubules are central to the alignment and segregation of chromosomes on the spindles. Unattached kinetochores are the primary signal to activate the spindle assembly checkpoint (SAC), a cell cycle surveillance pathway that delays exit from mitosis. The SAC detect the unstable kinetochore-microtubule attachment by a mechanism that is poorly understood. My findings revealed a possible role for mechanism changes in regulating K-MT attachment and activating SAC function.Previous research has highlighted Mpsl act upstream in activate SAC. But how Mpsl is target to the unsattached kinetochores is not clear. In my study, we provide evidence that the recruitment of Mpsl by Heel is essential for mitotic checkpoint activity. The recruitment is regulated by Heel N tail phosphorylation of Aurora B. The pull down experiment, which demonstated the CH domain of Heel was capable of interacting with thel-303region of Mpsl is consistent with the result of experssion of GFP-Hec1(l-196) in Hec1depletion cell could not recover Mpsl localization. Inhibition Aurora B by treating cell with small molecular inhibitor ZM447439prevent the accumulation of Mps1on kinetochore which implied us Aurora B may control Mps1localization by phosphorylating the Heel N-tail. Surprisingly, the Hec1-9D mutants strongly increased the amounts of Mpsl at kinetochore which9A mutant reduced. And the Hec1-9D mutant was coprecipitated by Mps1-KD. Based on data presented in this study, we postulate that the mitotic checkpoint relies on the N tail module of Hec1by Aurora B and that Mpsl mediated activation of the checkpoint relied on this module. In our modal, Heel N-tail increased the binding affinity of Mps1through phosphorylated Aurora B when the K-MT attachment was unstable, affecting SAC activated, whereas the SAC was inactivated when the nonphosphorylation-Hecl can not recruit enough Mps1in the proper bipolar spindle attachment.Histone methylation performs multiple functions such as DNA replication, transcription regulation, heterochromatin formation, and chromatin condensation. How this methylation gradient is orchestrated in the centromere during chromosome segregation is not known. Here we examine the temporal dynamics of protein methylation in the centromere by SUV39H1methyltransferase, a key mitotic regulator, using fluorescence resonance energy transfer-based sensors in living HeLa cells and immunofluorescence of native SUV39H1substrates. A quantitative analysis of methylation dynamics, using centromere-targeted sensors, reveals a temporal change during chromosome segregation. These dynamics result in an accurate chromosome congression to and alignment at the equator as an inhibition of methylation dynamics using SUV39H1inhibitor perturbs chromosome congression in living HeLa cells. Surprisingly, this inhibition of methylation results in a brief increase in Aurora B kinase activity and an enrichment of microtubule depolymerase MCAK in the centromere with a concomitant kinetochore-microtubule destabilization and a reduced tension across the sister kinetochores with ultimate chromosome misalignments. We reason that SUV39H1generates a gradient of methylation marks at the kinetochore that provides spatiotemporal information essential for accurate chromosome segregation in mitosis.