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Genetic analysis of LIN-12/Notch signaling in C. elegans has provided many insights into human biology. Activating missense mutations in the Negative Regulatory Region (NRR) of the ectodomain of LIN-12/Notch were first described in C. elegans, and similar mutations in human Notch were later found to cause T-cell acute lymphoblastic leukemia (T-ALL). The ubiquitin ligase sel-10/Fbw7 is the prototype of a conserved negative regulator of lin-12/Notch that was first defined by loss-of-function mutations that enhance lin-12 NRR-missense activity in C. elegans, and then demonstrated to regulate Notch activity in mammalian cells and to be a bona fide tumor suppressor in T-ALL. Here, we report the results of an RNAi screen of 248 C. elegans protein kinase-encoding genes with human orthologs for enhancement of a weakly activating NRR-missense mutation of lin-12 in the Vulval Precursor Cells. We identified, and validated, thirteen kinase genes whose loss led to increase lin-12 activity; eleven of these genes have never been implicated previously in regulating Notch activity in any system. Depleting the activity of five kinase genes (cdk-8, wnk-1, kin-3, hpo-11, and mig-15) also significantly enhanced the activity of a transgene in which heterologous sequences drive expression of the untethered intracellular domain of LIN-12, suggesting that they increase the activity or stability of the signal-transducing form of LIN-12/Notch. Precedents set by other regulators of lin-12/Notch defined through genetic interactions in C. elegans suggest that this new set of genes may include negative regulators that are functionally relevant to mammalian development and cancer.

Genetic analysis of LIN-12/Notch signaling in C . elegans has provided many insights into human biology. Activating missense mutations in the Negative Regulatory Region (NRR) of the ectodomain of LIN-12/Notch were first described in C. elegans , and similar mutations in human Notch were later found to cause T-cell acute lymphoblastic leukemia (T-ALL). The ubiquitin ligase sel-10 /Fbw7 is the prototype of a conserved negative regulator of lin-12 /Notch that was first defined by loss-of-function mutations that enhance lin-12 NRR-missense activity in C. elegans , and then demonstrated to regulate Notch activity in mammalian cells and to be a bona fide tumor suppressor in T-ALL. Here, we report the results of an RNAi screen of 248 C. elegans protein kinase-encoding genes with human orthologs for enhancement of a weakly activating NRR-missense mutation of lin-12 in the Vulval Precursor Cells. We identified, and validated, thirteen kinase genes whose loss led to increase lin-12 activity; eleven of these genes have never been implicated previously in regulating Notch activity in any system. Depleting the activity of five kinase genes ( cdk-8 , wnk-1 , kin-3 , hpo-11 , and mig-15 ) also significantly enhanced the activity of a transgene in which heterologous sequences drive expression of the untethered intracellular domain of LIN-12, suggesting that they increase the activity or stability of the signal-transducing form of LIN-12/Notch. Precedents set by other regulators of lin-12 /Notch defined through genetic interactions in C. elegans suggest that this new set of genes may include negative regulators that are functionally relevant to mammalian development and cancer., (Copyright © 2019 Deng et al.)