Connecting Ras and CTP synthase in Drosophila.

CTP synthase (CTPS), the enzyme responsible for the last step of de novo synthesis of CTP, forms filamentous structures termed cytoophidia in all three domains of life. Here we report that oncogenic Ras regulates cytoophidium formation in Drosophila intestines. Overexpressing active Ras induces elongate and abundant cytoophidia in intestinal stem cells (ISCs) and enteroblasts (EBs). Knocking-down CTPS in ISCs/EBs suppresses the over- proliferation phenotype induced by ectopic expression of active Ras. Moreover, disrupting cytoophidium formation increases the number of proliferating cells in the background of overexpressing active Ras. Therefore, our results demonstrate a link between Ras and CTPS.
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