In consequence, we next examined if p53 ubiquitination is affected by CDR1as. Co-expression of ubiquitin and MDM2 (the major E3 ubiquitinase of p53) significantly triggered ubiquitination of endogenous p53 protein in GBM cells, while MG132 treatment inhibited p53 degradation (Fig. 2g, h and Additional file 3: Figure S2D). Here, MDM2 is linked to glioblastoma.