PCNA and breast carcinoma: H1.2 depletion is seen to reduce the levels of several proteins essential to the cell cycle, including CDK2 (Cyclin-Dependent Kinase 2), MCM2 (Minichromosome Maintenance Complex Component 2), and PCNA (Proliferating Cell Nuclear Antigen), causing G1 phase arrest in the cell cycle of human breast cancer (BC) T47D cells (Sancho et al., 2008).