The Greatwall kinase safeguards the genome integrity by affecting the kinome activity in mitosis

Abstract

Progression through mitosis is balanced by the timely regulation of phosphorylation and dephosphorylation events ensuring the correct segregation of chromosomes before cytokinesis. This balance is regulated by the opposing actions of CDK1 and PP2A, as well as the Greatwall kinase/MASTL. MASTL is commonly overexpressed in cancer, which makes it a potential therapeutic anticancer target. Loss of Mastl induces multiple chromosomal errors that lead to the accumulation of micronuclei and multilobulated cells in mitosis. Our analyses revealed that loss of Mastl leads to chromosome breaks and abnormalities impairing correct segregation. Phospho-proteomic data for Mastl knockout cells revealed alterations in proteins implicated in multiple processes during mitosis including double-strand DNA damage repair. In silico prediction of the kinases with affected activity unveiled NEK2 to be regulated in the absence of Mastl. We uncovered that, RAD51AP1, involved in regulation of homologous recombination, is phosphorylated by NEK2 and CDK1 but also efficiently dephosphorylated by PP2A/B55. Our results suggest that MastlKO disturbs the equilibrium of the mitotic phosphoproteome that leads to the disruption of DNA damage repair and triggers an accumulation of chromosome breaks even in noncancerous cells.

Spatiotemporal coordination of Greatwall-Endos-PP2A promotes mitotic progression

“…By this mechanism, phosphorylated substrates of mitotic kinases in the nucleus are presumably protected from premature dephosphorylation by PP2A-Tws between NEBD and mitotic exit. The identity of these substrates is still unclear, but they likely include the spindle assembly checkpoint kinase Mps1 and factors of the DNA damage-repair machinery ( Bisteau et al, 2020 ; Diril et al, 2016 ). Moreover, it would be interesting to explore if the spatiotemporal mechanism described here is essential for the ability of Gwl and Endosulfines to promote the G2/M transition in various systems (see Introduction).…”

In Cellulo Kinase Screen Identifies Potential MASTL Substrates

“…MASTL (microtubule-associated serine/threonine kinase-like) is the human orthologue of Drosophila Greatwall (Gwl) kinase 1,2 , a protein essential for mitosis 3 . Since its discovery, MASTL has become known as a master regulator of mitotic entry and integrity [4][5][6][7] . More recently, its roles have expanded to include meiosis 8-10 , recovery from DNA damage [11][12][13] , DNA replication 14 , platelet maturation 15,16 , cell migration and actomyosin contraction 17 .…”

“…Several recent efforts have been made to identify potential MASTL substrates with con icting results. Work by Bisteau et al 7 , identi ed 101 mitotic proteins that were dephosphorylated upon MASTL knockout in immortalized mouse embryonic fibroblasts (MEFs). Of these 6 were weakly phosphorylated in vitro by puri ed MASTL, but no decrease was observed using kinase dead MASTL, indicating that none are MASTL substrates 7 .…”

Discovery and Characterization of a Novel MASTL Inhibitor MKI-2 Targeting MASTL-PP2A in Breast Cancer Cells and Oocytes

“…Microtubule-associated serine/threonine kinase-like (MASTL), also known as Greatwall kinase, is a key mitotic kinase that regulates mitotic progression and maintains mitotic integrity [ 1 , 2 , 3 ]. MASTL controls the inactivation of the protein phosphatase 2A complex (PP2A-B55) by the directly phosphorylating its substrates, such as α-endosulfine (ENSA) and cAMP-regulated phosphoprotein 19, during mitosis and meiosis in mammalian somatic cells and oocytes, respectively [ 4 , 5 , 6 , 7 , 8 , 9 ].…”

“…Recent studies suggested that MASTL acts as an oncogenic kinase by inactivating tumor suppressive PP2A-B55 complex in breast cancer cells [11][12][13], thereby regulating various oncogenic properties, such as cellular transformation, chromosome instability, and Pharmaceuticals 2021, 14, 647. https://doi.org/10.3390/ph14070647 https://www.mdpi.com/journal/pharmaceuticals Pharmaceuticals 2021, 14, 647 2 of 12 metastasis [3,14,15]. MASTL targeting has reduced tumor growth in various in vitro and in vivo tumor models [13,16].…”