Proliferating cell nuclear antigen, PCNA, is a cofactor of DNA polymerase delta, and is expressed in the nuclei of cells during the DNA synthesis phase (S phase) of the cell cycle.
PCNA is involved in eukaryotic DNA replication. PCNA is conserved in chimpanzee, dog, cow, mouse, rat, chicken, zebrafish, fruit fly, mosquito, S. pombe, S. cerevisiae, K. lactis, E. gossypii, M. grisea, N. crassa, A. thaliana, and rice.
Human PCNA with 261 amino acids share 97% identity with rodent homologs and 36% identity with yeast homologs. PCNA is not a good loading control for non-proliferating cells or cells with anti-proliferation treatment.