RING1 and glioblastoma: EZH2 is the catalytic sub-unit of the PRC2 and is required for H3K27me3 deposition and maintenance.49 On the other hand, the BMI1//RING1 complex regulates H2Aub deposition, possibly also directly or indirectly affecting H3K9me3 levels in normal somatic cells.50 Consistently, we found that treatment of GBM spheres (GBM1205) with PTC596 for 24 h resulted in robust down-regulation of H2Aub levels (Fig. 3a).