6eht | pdb_00006eht
Modulation of PCNA sliding surface by p15PAF suggests a suppressive mechanism for cisplatin-induced DNA lesion bypass by pol eta holoenzyme
Structural highlights
Function[PCNA_HUMAN] Auxiliary protein of DNA polymerase delta and is involved in the control of eukaryotic DNA replication by increasing the polymerase's processibility during elongation of the leading strand. Induces a robust stimulatory effect on the 3'-5' exonuclease and 3'-phosphodiesterase, but not apurinic-apyrimidinic (AP) endonuclease, APEX2 activities. Has to be loaded onto DNA in order to be able to stimulate APEX2. Plays a key role in DNA damage response (DDR) by being conveniently positioned at the replication fork to coordinate DNA replication with DNA repair and DNA damage tolerance pathways. Acts as a loading platform to recruit DDR proteins that allow completion of DNA replication after DNA damage and promote postreplication repair: Monoubiquitinated PCNA leads to recruitment of translesion (TLS) polymerases, while 'Lys-63'-linked polyubiquitination of PCNA is involved in error-free pathway and employs recombination mechanisms to synthesize across the lesion.[1] [2] [PAF15_HUMAN] PCNA-binding protein that acts as a regulator of DNA repair during DNA replication. Following DNA damage, the interaction with PCNA is disrupted, facilitating the interaction between monoubiquitinated PCNA and the translesion DNA synthesis DNA polymerase eta (POLH) at stalled replisomes, facilitating the bypass of replication-fork-blocking lesions. Also acts as a regulator of centrosome number.[3] [4] Publication Abstract from PubMedp15PAF 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, p15PAF traverses the PCNA ring via an extended PIP-box that contacts the sliding surface. Here, we probed the atomic-scale structure of p15PAF-PCNA-DNA ternary complexes. Crystallography and MD simulations show that, when p15PAF occupies two subunits of the PCNA homotrimer, DNA within the ring channel binds the unoccupied subunit. The structure of PCNA-bound p15PAF in the absence and presence of DNA is invariant, and solution NMR confirms that DNA does not displace p15PAF from the ring wall. Thus, p15PAF 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 delta). This constraint, however, may need to be released for efficient DNA lesion bypass by the translesion synthesis polymerase (pol eta). Accordingly, our biochemical data show that p15PAF impairs primer synthesis by pol eta-PCNA holoenzyme against both damaged and normal DNA templates. In light of our findings, we discuss the possible mechanistic roles of p15PAF in DNA replication and suppression of DNA lesion bypass. p15PAF binding to PCNA modulates the DNA sliding surface.,De March M, Barrera-Vilarmau S, Crespan E, Mentegari E, Merino N, Gonzalez-Magana A, Romano-Moreno M, Maga G, Crehuet R, Onesti S, Blanco FJ, De Biasio A Nucleic Acids Res. 2018 Aug 8. pii: 5068262. doi: 10.1093/nar/gky723. PMID:30102405[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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