P15PAF binding to PCNA modulates the DNA sliding surface. Issue 18 (8th August 2018)

• Record Type: Journal Article
• Authors: De March, Matteo; Barrera-Vilarmau, Susana; Crespan, Emmanuele; Mentegari, Elisa; Merino, Nekane; Gonzalez-Magaña, Amaia; Romano-Moreno, Miguel; Maga, Giovanni; Crehuet, Ramon; Onesti, Silvia; Blanco, Francisco J; De Biasio, Alfredo
• Is Part Of: Nucleic acids research. Volume 46:Issue 18(2018)
• Page Start: 9816
• Page End: 9828
• Publication Date: 2018-08-08
• Subjects: Nucleic acids -- Periodicals; Molecular biology -- Periodicals; 572.805
• DOI: 10.1093/nar/gky723
• Languages: English
• ISSNs: 0305-1048

Abstract

Abstract: p15 PAF is an oncogenic intrinsically disordered protein that regulates DNA replication and lesion bypass by interacting with the human sliding clamp PCNA. In the absence of DNA, p15 PAF traverses the PCNA ring via an extended PIP-box that contacts the sliding surface. Here, we probed the atomic-scale structure of p15 PAF –PCNA–DNA ternary complexes. Crystallography and MD simulations show that, when p15 PAF occupies two subunits of the PCNA homotrimer, DNA within the ring channel binds the unoccupied subunit. The structure of PCNA-bound p15 PAF in the absence and presence of DNA is invariant, and solution NMR confirms that DNA does not displace p15 PAF from the ring wall. Thus, p15 PAF reduces the available sliding surfaces of PCNA, and may function as a belt that fastens the DNA to the clamp during synthesis by the replicative polymerase (pol δ). This constraint, however, may need to be released for efficient DNA lesion bypass by the translesion synthesis polymerase (pol η). Accordingly, our biochemical data show that p15 PAF impairs primer synthesis by pol η–PCNA holoenzyme against both damaged and normal DNA templates. In light of our findings, we discuss the possible mechanistic roles of p15 PAF in DNA replication and suppression of DNA lesion bypass.