Proliferating cell nuclear antigen (PCNA) is a key protein involved in DNA replication, repair, and cell cycle regulation. Originally identified as a DNA sliding clamp that enhances the processivity of replicative DNA polymerases, PCNA has since been shown to interact with a wide range of proteins involved in various cellular processes, including DNA repair, chromatin remodeling, and cell cycle control. PCNA forms a homotrimer with a ring-like structure that allows it to encircle and slide along DNA, facilitating the coordinated action of multiple proteins. The interaction of PCNA with its partners is crucial for the proper execution of DNA replication and repair, as well as for the regulation of the cell cycle. PCNA binds to numerous proteins through specific motifs, such as the PIP-box and the newly identified KA-box, and these interactions are essential for the recruitment and coordination of these proteins at specific sites. PCNA also plays a role in DNA damage response, where it helps in the recruitment of repair enzymes and in the regulation of DNA synthesis. In addition, PCNA is involved in cell cycle control, where it interacts with cyclin-CDK complexes and the CDK inhibitor p21. These interactions help regulate the progression of the cell cycle and ensure proper DNA replication and repair. PCNA's ability to interact with a variety of proteins makes it a central hub in the coordination of DNA-related processes, highlighting its essential role in maintaining genomic stability and cellular function.Proliferating cell nuclear antigen (PCNA) is a key protein involved in DNA replication, repair, and cell cycle regulation. Originally identified as a DNA sliding clamp that enhances the processivity of replicative DNA polymerases, PCNA has since been shown to interact with a wide range of proteins involved in various cellular processes, including DNA repair, chromatin remodeling, and cell cycle control. PCNA forms a homotrimer with a ring-like structure that allows it to encircle and slide along DNA, facilitating the coordinated action of multiple proteins. The interaction of PCNA with its partners is crucial for the proper execution of DNA replication and repair, as well as for the regulation of the cell cycle. PCNA binds to numerous proteins through specific motifs, such as the PIP-box and the newly identified KA-box, and these interactions are essential for the recruitment and coordination of these proteins at specific sites. PCNA also plays a role in DNA damage response, where it helps in the recruitment of repair enzymes and in the regulation of DNA synthesis. In addition, PCNA is involved in cell cycle control, where it interacts with cyclin-CDK complexes and the CDK inhibitor p21. These interactions help regulate the progression of the cell cycle and ensure proper DNA replication and repair. PCNA's ability to interact with a variety of proteins makes it a central hub in the coordination of DNA-related processes, highlighting its essential role in maintaining genomic stability and cellular function.