BMI1 and acute myeloid leukemia: These variants are responsible for the deposition of the H2A mono-ubiquitination, whereas the canonical PRC1 is more involved in chromatin compaction and looping.86 A key component of the canonical PRC1 complex is the PCGF protein BMI1, which fuels the E3 ligase activity of the RING proteins in the deposition of H2A mono-ubiquitination.87 PRC1 function is hijacked in AML to repress differentiation-associated programs, contributing to enhanced self-renewal of the leukemic cells88 (Figure 2B).