SUMOylation of the lysine-less tumor suppressor p14ARF counters ubiquitylation-dependent degradation.

p14ARF is a lysine-less tumor suppressor that enhances SUMOylation of its interactors. Although p14ARF is known to interact with the E2 SUMO conjugating enzyme UBC9, the link between ARF and SUMOylation is poorly understood and the potential impact of SUMOylation on p14ARF is unknown. Here we show that SUMO2 conjugates to the N-terminus of p14ARF and stabilizes it. Either depleting UBC9 or pharmacologically inhibiting SUMOylation, induces p14ARF degradation. In contrast, blocking ubiquitination or NEDDylation, with TAK-243 or MLN4924/Pevonedistat respectively, increases p14ARF SUMOylation and restores p14ARF levels when SUMOylation is blocked. Treatment with MLN4924 also causes p14ARF-dependent mRNA upregulation of the SUMOylation components SUMO1, SUMO2, and UBC9, globally augmenting SUMOylation. Finally, p14ARF contributes to MLN4924-driven cytotoxicity of prostate cancer cells. Our results provide evidence that, despite lacking lysine, p14ARF is SUMOylated and this modification is critical to counter ubiquitin driven degradation and establishes a new link between inhibition of NEDDylation and SUMOylation.