NMR Mapping of PCNA Interaction with Translesion Synthesis DNA Polymerase Rev1 Mediated by Rev1-BRCT Domain

Rev1 is a Y-family translesion synthesis (TLS) DNA polymerase involved in bypass replication across sites of DNA damage and postreplicational gap filling. In the process of TLS, high-fidelity replicative DNA polymerases stalled by DNA damage are replaced by error-prone TLS enzymes responsible for the majority of mutagenesis in eukaryotic cells. The polymerase exchange that gains low-fidelity TLS polymerases access to DNA is mediated by their interactions with proliferating cell nuclear antigen (PCNA). Rev1 stands alone from other Y-family TLS enzymes since it lacks the consensus PCNA-interacting protein box (PIP-box) motif, instead utilizing other modular domains for PCNA binding. Here we report solution NMR structure of an 11-kDa BRCA1 C-terminus (BRCT) domain from Saccharomyces cerevisiae Rev1 and demonstrate with the use of transverse relaxation optimized spectroscopy (TROSY) NMR methods that Rev1-BRCT domain directly interacts with an 87-kDa PCNA in solution. The domain adopts alpha/beta fold (beta 1-alpha 1-beta 2-beta 3-alpha 2-beta 4-alpha 3-alpha 4) typical for BRCT domain superfamily. PCNA-binding interface of the Rev1-BRCT domain comprises conserved residues of the outer surface of the alpha 1-helix and the alpha 1-beta 1, beta 2-beta 3 and beta 3-alpha 2 loops. On the other hand, Rev1-BRCT binds to the inter-domain region of PCNA that overlaps with the binding site for the PIP-box motif. Furthermore, Rev1-BRCT domain bound to PCNA can be displaced by increasing amounts of the PIP-box peptide from TLS DNA polymerase pol eta, suggesting that Rev1-BRCT and pol eta PIP-box interactions with the same PCNA monomer are mutually exclusive. These results provide structural insights into PCNA recognition by TLS DNA polymerases that help better understand TLS regulation in eukaryotes. (C) 2013 Elsevier Ltd. All rights reserved.