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Arabidopsis CASEIN KINASE 2 controls Aluminium toxicity and phosphate deficiency through control of the DNA damage response

ABSTRACT: Aluminum (Al) toxicity and phosphate (Pi) limitation are widespread chronic abiotic and mutually enhancing stresses that profoundly affect crop yield. Both stresses causes a strong inhibition of root growth due to a progressive exhaustion of the stem cell niche. Here we report on a CASEIN KINASE 2 (CK2) inhibitor identified by its capability to maintain a functional root stem cell niche under Al toxic conditions. CK2 operates through phosphorylation of the cell cycle checkpoint activator SUPPRESSOR OF GAMMA RADIATION 1 (SOG1), priming its activity under DNA damaging conditions. In addition to yielding Al tolerance, both CK2 and SOG1 inactivation result in resistance to phosphate starvation, revealing the existence of a low phosphate induced cell cycle checkpoint that depends on the DNA damage activator ATAXIA-TELANGIECTASIA MUTATED (ATM). Overall, our data reveal an important physiological role for the plant DNA damage response pathway under agricultural limiting growth conditions and opening new avenues to cope with the problem of Pi limitation. SOG1 can be phosphorylated by both ATM and ATR (Sjogren et al., 2015; Yoshiyama et al., 2017). ATM phosphorylation of SOG1 can occur at five different S/TQ sites upon treatment with double-stand break inducing compounds such as zeocin. This phosphorylation is important for its activity, as demonstrated by the inability of a phosphor-mutant allele to complement the sog1 mutant. In addition to the ATM/ATR-dependent phosphorylation sites, 11 putative CK2 phosphorylation sites [T/SXXE/D, with S or T serving as the phospho-acceptor site (Meggio and Pinna, 2003)] are found within the full length SOG1 proteins. Among these, four sites are conserved among orthologous proteins, stressing their potential importance to protein function. Of these, three cluster at the extreme C-terminus of SOG1, which also is also the location of the ATM/ATR phosphorylation sites. To test putative phosphorylation of any of these sites, TAP-tagged SOG1 protein was extracted and purified from cell cultures and subjected to phosphorylation analysis.

INSTRUMENT(S): LTQ Orbitrap Elite

ORGANISM(S): Arabidopsis Thaliana (mouse-ear Cress)

TISSUE(S): Plant Cell, Cell Culture

SUBMITTER: Dominique Eeckhout

LAB HEAD: Lieven De Veylder

PROVIDER: PXD018727 | Pride | 2021-03-29

REPOSITORIES: Pride

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Project description:The cell division cycle is tightly controlled in normal cells. Cancer cells are characterized by deregulation in cell division cycle, which is associated with increased DNA replication and elevated cellular proliferation. Recently, genetic studies indicate that cyclin dependent kinases CDK2, CDK4 and CDK6 are not essential for the mammalian cell cycle, instead, they are only required for the proliferation of specific cell types.Thus, targeting the activities of CDK2, CDK4 and CDK6 may be a promising approach for cancer treatment. Rocaglamides (Roc) (= Flavaglines), derived from the traditional Chinese medicinal plant Aglaia, are a group of naturally occurring herbal chemicals characterized by a cyclopenta[b]benzofurans skeleton. A number of Roc derivatives have been found to have potent inhibitory effects on tumor growth with IC50 concentrations at the nM rages. Roc-mediated inhibition of proliferation was first found to be associated with inhibition of protein synthesis in 1998. In this study, using the representative Roc-A compound we revealed a novel mechanistic function of Roc. We show that Roc-A induces rapid activation of ATM (ataxiatelangiectasia mutated) and ATR (ataxia-telangiectasia and Rad3-related) kinases. Activated ATM and ATR in turn activate the downstream checkpoint kinases CHK1 and CHK2. The latter then phosphorylate Cdc25A that leads to a phosphorylation-mediated degradation of Cdc25A. Usually, ATR and ATM are activated in response to DNA damage. However, in this study we show that Roc-A does not directly induce DNA breaks. To elucidate the molecular mechanism by which Roc-A activates ATM and ATR we performed a time-resolved microarray analysis to compare Roc-A-inducible genes in malignant vs. normal T lymphocytes. Based on the dynamic gene responses we found that Roc-A stimulates in Jurkat, but not in normal T lymphocytes, a set of genes responsive to DNA damage and nucleotide excision repair. This finding provides a hint of the molecular bases for Roc-induced activation of ATM and ATR. This finding also revealed a new scope for cancer treatment using Roc-A. The isolation time points for Roc A treated D6 T-cells were recorded at t=[1,2,3,4,6,8,10,14,20,28,36] hours after stimulation. Post-stimulation time points for Jurkat cells are t=[0.5,1,2,3,4,5,6,7,8,10,12,14,16,20,24,28,32,36]. Unstimulated control time points were taken at t=[0,4,10,16,24,36] hours for Jurkat cells at t=[0,6,14,24,36] hours.

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Arabidopsis CASEIN KINASE 2 controls Aluminium toxicity and phosphate deficiency through control of the DNA damage response

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