Proliferating cell nuclear antigen (PCNA); functions as the sliding replication clamp for DNA polymerase δ; may function as docking site for other proteins required for mitotic and meiotic chromosomal DNA replication and for DNA repair; PCNA ubiquitination at K164 plays crucial role during Okazaki fragment processing; Leu164 is essential for stable complex formation with replicative DNA polymerase δ