7nv1
From Proteopedia
Human Pol Kappa holoenzyme with Ub-PCNA
Structural highlights
FunctionPOLK_HUMAN DNA polymerase specifically involved in DNA repair. Plays an important role in translesion synthesis, where the normal high-fidelity DNA polymerases cannot proceed and DNA synthesis stalls. Depending on the context, it inserts the correct base, but causes frequent base transitions, transversions and frameshifts. Lacks 3'-5' proofreading exonuclease activity. Forms a Schiff base with 5'-deoxyribose phosphate at abasic sites, but does not have lyase activity.[1] [2] [3] [4] [5] [6] [7] Publication Abstract from PubMedY-family DNA polymerase kappa (Pol kappa) can replicate damaged DNA templates to rescue stalled replication forks. Access of Pol kappa to DNA damage sites is facilitated by its interaction with the processivity clamp PCNA and is regulated by PCNA mono-ubiquitylation. Here, we present cryo-EM reconstructions of human Pol kappa bound to DNA, an incoming nucleotide, and wild type or mono-ubiquitylated PCNA (Ub-PCNA). In both reconstructions, the internal PIP-box adjacent to the Pol kappa Polymerase-Associated Domain (PAD) docks the catalytic core to one PCNA protomer in an angled orientation, bending the DNA exiting the Pol kappa active site through PCNA, while Pol kappa C-terminal domain containing two Ubiquitin Binding Zinc Fingers (UBZs) is invisible, in agreement with disorder predictions. The ubiquitin moieties are partly flexible and extend radially away from PCNA, with the ubiquitin at the Pol kappa-bound protomer appearing more rigid. Activity assays suggest that, when the internal PIP-box interaction is lost, Pol kappa is retained on DNA by a secondary interaction between the UBZs and the ubiquitins flexibly conjugated to PCNA. Our data provide a structural basis for the recruitment of a Y-family TLS polymerase to sites of DNA damage. Cryo-EM structure of human Pol kappa bound to DNA and mono-ubiquitylated PCNA.,Lancey C, Tehseen M, Bakshi S, Percival M, Takahashi M, Sobhy MA, Raducanu VS, Blair K, Muskett FW, Ragan TJ, Crehuet R, Hamdan SM, De Biasio A Nat Commun. 2021 Oct 19;12(1):6095. doi: 10.1038/s41467-021-26251-6. PMID:34667155[8] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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