Supplemental Material for Kushnir et al., 2020

Excessive RTK signaling, often caused by activating mutations in Ras, Raf and/or MEK, occurs in most human tumors. Intriguingly, confirmed cancer-driver mutations in the downstream effector kinase, ERK, have not been reported. To test if active ERK mutants can function as oncoproteins, we introduced an activating mutation, originally identified in a yeast ERK, into the single <i>Drosophila</i> ERK. We find that this mutation renders ERK catalytically active independently of upstream signaling, and that its expression induces extensive over-proliferation and hyperplastic tumor formation <i>in vivo</i>. Thus, some human ERK1/2 mutations identified in patient-derived tumours may actually represent overlooked oncogenic, cancer-causing mutations.<br>