Polycomb proteins control proliferation and transformation independently of cell cycle checkpoints by regulating DNA replication

Polycomb (PcG) proteins are known to promote cell proliferation by silencing expression of the tumour suppressor Ink4A-Arf. Piunti et al. show that PcG proteins also regulate tumour progression independently of this role, revealing a requirement for PRC1 and PRC2 in replication fork progression.