UV Irradiation Triggers Cylindromatosis Translocation, Modification, and Degradation in a Proteasome-Independent Manner

The tumor suppressor, cylindromatosis (CYLD), is a negative regulator of NF-κB signaling by removing lysine 63-linked ubiquitin chains from multiple NF-κB signaling components, including TRAF2, TRAF6, and NEMO. How CYLD itself is regulated, however, remains yet to be characterized. In this study, we present the first evidence that UV irradiation is able to induce CYLD translocation from the cytoplasm to microtubules and that the cytoskeleton-associated CYLD is subject to posttranslational modification and degradation in a proteasome-independent manner. By immunostaining, we found that CYLD displayed microtubule-like filament localization under ultraviolet (UV) irradiation. Further studies revealed that the cytoskeleton-associated CYLD underwent posttranslational modification, which in turn contributed to CYLD degradation in an unknown manner, distinct from proteasome-mediated degradation under normal conditions. Collectively, our data suggest that UV-induced CYLD degradation might serve as an underlying mechanism for UV-induced NF-κB pathway activation.