Photo-activatable Ub-PCNA probes reveal new structural features of the Saccharomyces cerevisiae Pol?/PCNA complex.

The Y-family DNA polymerase ? (Pol?) is critical for the synthesis past damaged DNA nucleotides in yeast through translesion DNA synthesis (TLS). TLS is initiated by monoubiquitination of proliferating cell nuclear antigen (PCNA) and the subsequent recruitment of TLS polymerases. Although individual structures of the Pol? catalytic core and PCNA ...
have been solved, a high-resolution structure of the complex of Pol?/PCNA or Pol?/monoubiquitinated PCNA (Ub-PCNA) still remains elusive, partly due to the disordered Pol? C-terminal region and the flexibility of ubiquitin on PCNA. To circumvent these obstacles and obtain structural insights into this important TLS polymerase complex, we developed photo-activatable PCNA and Ub-PCNA probes containing a p-benzoyl-L-phenylalanine (pBpa) crosslinker at selected positions on PCNA. By photo-crosslinking the probes with full-length Pol?, specific crosslinking sites were identified following tryptic digestion and tandem mass spectrometry analysis. We discovered direct interactions of the Pol? catalytic core and its C-terminal region with both sides of the PCNA ring. Model building using the crosslinking site information as a restraint revealed multiple conformations of Pol? in the polymerase complex. Availability of the photo-activatable PCNA and Ub-PCNA probes will also facilitate investigations into other PCNA-containing complexes important for DNA replication, repair and damage tolerance.
Mesh Terms:
Benzophenones, DNA, DNA Replication, DNA-Binding Proteins, DNA-Directed DNA Polymerase, Macromolecular Substances, Mutation, Phenylalanine, Proliferating Cell Nuclear Antigen, Protein Binding, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins, Ubiquitin
Nucleic Acids Res
Date: Dec. 20, 2020
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