UBR5 and melanoma: In addition, to investigate whether CSN6 controls the ubiquitination and degradation of the E3 ligase UBR5 to stabilize CDK9, in vivo ubiquitination assays were performed and found that CSN6 increased UBR5 ubiquitination levels and decreased CDK9 ubiquitination levels in melanoma cells and 293FT cells (Fig. 5F, G).