Eukaryotic translesion polymerases and their roles and regulation in DNA damage tolerance

Abstract

DNA repair and DNA damage tolerance machineries are crucial to overcome the vast array of DNA damage that a cell encounters during its lifetime. In this review, we summarize the current state of knowledge about the eukaryotic DNA damage tolerance pathway translesion synthesis (TLS), a process in which specialized DNA polymerases replicate across from DNA lesions. TLS aids in resistance to DNA damage, presumably by restarting stalled replication forks or filling in gaps that remain in the genome due to the presence of DNA lesions. One consequence of this process is the potential risk of introducing mutations. Given the role of these translesion polymerases in mutagenesis, we discuss the significant regulatory mechanisms that control the five known eukaryotic translesion polymerases: Rev1, Pol zeta, Pol kappa, Pol eta, and Pol iota.

FIG. 1.

DNA damage repair and bypass mechanisms. (A) DNA damage results in breakage of the sugar-phosphate backbone, DNA base loss (indicated by a gap in the DNA), or base alterations (as indicated by the gray star). This damage can be repaired/removed from the DNA strand or tolerated, in which case the DNA lesion remains but cellular processes continue. (B) An example of the DNA damage tolerance mechanism TLS, whereby a damaged DNA template is replicated using a TLS polymerase and the damage remains in the genome. A more detailed mechanism of TLS is described in the text and represented in Fig. 4.

FIG. 2.

Crystal structures of two Y family polymerases. (A) Cocrystal structure of the S. cerevisiae TLS Pol η with a DNA template containing a cisplatin cross-link. The structure is oriented to highlight the right-hand architecture as seen in both TLS and replicative polymerases. (Based on data from reference and the RSCB protein data bank [PDB ID number 2r8j].) (B) Close-up view of the unique lesion bypass mechanism of Rev1 from S. cerevisiae. Highlighted are the novel leucine (L325) that helps to flip out the template guanine and the catalytic arginine (R324) that hydrogen bonds to stabilize the incoming dCTP. The domains of Rev1 are colored as in panel A, with the exception of the DNA, which is shown in black. (Based on data from reference and the RCSB protein data bank [PDB ID number 2aq4].)

FIG. 3.

Cartoon representation of the protein domains in the human B family TLS polymerase ζ and the Y family TLS polymerases Rev1, κ, ι, and η. aa, amino acids. (Based on data from references and .)

FIG. 4.

Two nonexclusive models for TLS: the polymerase-switching model (A) and the gap-filling model (B). See text for details.