PMID: 26503230

Authors:

Lau WC, Li Y, Zhang Q, Huen MS

Title:

Molecular architecture of the Ub-PCNA/Pol eta complex bound to DNA.

Journal:

Sci Rep. 2015 Oct 27;5:15759. doi: 10.1038/srep15759.

Abstract:

Translesion synthesis (TLS) is the mechanism by which DNA polymerases replicate through unrepaired DNA lesions. TLS is activated by monoubiquitination of the homotrimeric proliferating cell nuclear antigen (PCNA) at lysine-164, followed by the switch from replicative to specialized polymerases at DNA damage sites. Pol eta belongs to the Y-Family of specialized polymerases that can efficiently bypass UV-induced lesions. Like other members of the Y-Family polymerases, its recruitment to the damaged sites is mediated by the interaction with monoubiquitinated PCNA (Ub-PCNA) via its ubiquitin-binding domain and non-canonical PCNA-interacting motif in the C-terminal region. The structural determinants underlying the direct recognition of Ub-PCNA by Pol eta, or Y-Family polymerases in general, remain largely unknown. Here we report a structure of the Ub-PCNA/Pol eta complex bound to DNA determined by single-particle electron microscopy (EM). The overall obtained structure resembles that of the editing PCNA/PolB complex. Analysis of the map revealed the conformation of ubiquitin that binds the C-terminal domain of Pol eta. Our present study suggests that the Ub-PCNA/Pol eta interaction requires the formation of a structured binding interface, which is dictated by the inherent flexibility of Ub-PCNA.