PCNA Ser46-Leu47 residues are crucial in preserving genomic integrity

Proliferating cell nuclear antigen (PCNA) is a maestro of DNA replication. PCNA forms a homotrimer and interacts with various proteins, such as DNA polymerases, DNA ligase I (LIG1), and flap endonuclease 1 (FEN1) for faithful DNA replication. Here, we identify the crucial role of Ser46-Leu47 residues of PCNA in maintaining genomic integrity using in vitro, and cell-based assays and structural prediction. The predicted PCNA(ΔSL47) structure shows the potential distortion of the central loop and reduced hydrophobicity. PCNA(ΔSL47) shows a defective interaction with PCNA(WT) leading to defects in homo-trimerization in vitro. PCNA(ΔSL47) is defective in the FEN1 and LIG1 interaction. PCNA ubiquitination and DNA-RNA hybrid processing are defective in PCNA(ΔSL47)-expressing cells. Accordingly, PCNA(ΔSL47)-expressing cells exhibit an increased number of single-stranded DNA gaps and higher levels of γH2AX, and sensitivity to DNA-damaging agents, highlighting the importance of PCNA Ser46-Leu47 residues in maintaining genomic integrity.