Casein Kinase II is Required for Proper Cell Division and Acts as a Negative Regulator of Centrosome Duplication inC. elegansEmbryos

Abstract

Summary statementThe conserved protein kinase CK2 negatively regulates centrosome assembly and is required for proper cell cycle progression and cytokinesis in early C. elegans embryos.AbstractCentrosomes are the primary microtubule-organizing centers that orchestrate microtubule dynamics during the cell cycle. The correct number of centrosomes is pivotal for establishing bipolar mitotic spindles that ensure accurate segregation of chromosomes. Thus, centrioles must duplicate once per cell cycle, one daughter per mother centriole, the process of which requires highly coordinated actions among core factors and modulators. Protein phosphorylation is shown to regulate the stability, localization and activity of centrosome proteins. Here, we report the function of Casein Kinase II (CK2) in early C. elegans embryos. The catalytic subunit (KIN-3/CK2α) of CK2 localizes to nuclei, centrosomes and midbodies. Inactivating CK2 leads to cell division defects, including chromosome missegregation, cytokinesis failure and aberrant centrosome behavior. Furthermore, depletion or inhibiting kinase activity of CK2 results in elevated ZYG-1 levels at centrosomes, restoring centrosome duplication and embryonic viability to zyg-1 mutants. Our data suggest that CK2 functions in cell division and negatively regulates centrosome duplication in a kinase-dependent manner.

APC/CFZR-1Controls ZYG-1 Levels to Regulate Centrosome Assembly

“…S4C), Alexa Fluor 488 and 568 secondary antibodies (ThermoFisher, #A11001, A11004, A11006, A11034, A11036). Confocal microscopy was performed (Medley et al, 2017b) using a Nikon Eclipse Ti-U microscope equipped with a Plan Apo 60×1.4 NA lens, a Spinning Disk Confocal (CSU X1) and a Photometrics Evolve 512 camera. MetaMorph software (Molecular Devices, Sunnyvale, CA, USA) was used for image acquisition and quantification of the fluorescence intensity, and Adobe Photoshop/Illustrator 2020 for image processing.…”

Site-Specific Phosphorylation of ZYG-1 Regulates ZYG-1 Stability and Centrosome Number

“…Several C. elegans genes have been identified that regulate ZYG-1 activity. Genetic screens for suppressors of zyg-1 revealed that ZYG-1 activity in centrosome assembly is modulated through several mechanisms, including transcription, RNA binding, proteolysis, and protein phosphorylation [25][26][27][28][29] . Studies in C. elegans have shown that protein phosphorylation influences cellular and centrosomal levels of ZYG-1, which is critical for normal centrosome number and microtubule-nucleating activity 25,[29][30][31] .…”

“…Genetic screens for suppressors of zyg-1 revealed that ZYG-1 activity in centrosome assembly is modulated through several mechanisms, including transcription, RNA binding, proteolysis, and protein phosphorylation [25][26][27][28][29] . Studies in C. elegans have shown that protein phosphorylation influences cellular and centrosomal levels of ZYG-1, which is critical for normal centrosome number and microtubule-nucleating activity 25,[29][30][31] . PP2A SUR-6/B55 exhibits a strong genetic interaction with ZYG-1 and SAS-5, and PP2A SUR-6/B55 -dependent dephosphorylation positively affects abundance of ZYG-1 and SAS-5, suggesting that PP2A SUR-6/B55 -dependent dephosphorylation stabilizes ZYG-1 and SAS-5 by protecting these proteins from proteasomal destruction 31 .…”

“…In C. elegans, Casein Kinase II (CK2) has been shown to negatively regulate centrosome duplication 25 . CK2 typically functions as a tetrameric holoenzyme comprising two catalytic (CK2α) and two regulatory (CK2β) subunits.…”

“…CK2 typically functions as a tetrameric holoenzyme comprising two catalytic (CK2α) and two regulatory (CK2β) subunits. The C. elegans genome contains the kin-3 and kin-10 genes that encode for the CK2α and CK2β subunits, respectively 33,34 , and CK2 functions in various cellular processes [35][36][37][38][39][40][41][42][43] including microRNA targeting 42 and cell division 25 . CK2 is an evolutionarily conserved serine/threonine protein kinase and targets numerous substrates (>500) in diverse cellular processes 44,45 .…”