Beyond translesion synthesis: polymerase κ fidelity as a potential determinant of microsatellite stability.
Microsatellite DNA synthesis represents a significant component of human genome replication that must occur faithfully. However, yeast replicative DNA polymerases do not possess high fidelity for microsatellite synthesis. We hypothesized that the structural features of Y-family polymerases that facilitate accurate translesion synthesis may promote accurate microsatellite synthesis. We compared human polymerases κ (Pol κ) and η (Pol η) fidelities to that of replicative human polymerase δ holoenzyme (Pol δ4), using the in vitro HSV-tk assay. Relative polymerase accuracy for insertion/deletion (indel) errors within 2-3 unit repeats internal to the HSV-tk gene concurred with the literature: Pol δ4 >> Pol κ or Pol η. In contrast, relative polymerase accuracy for unit-based indel errors within [GT](10) and [TC](11) microsatellites was: Pol κ ≥ Pol δ4 > Pol η. The magnitude of difference was greatest between Pols κ and δ4 with the [GT] template. Biochemically, Pol κ displayed less synthesis termination within the [GT] allele than did Pol δ4. In dual polymerase reactions, Pol κ competed with either a stalled or moving Pol δ4, thereby reducing termination. Our results challenge the ideology that pol κ is error prone, and suggest that DNA polymerases with complementary biochemical properties can function cooperatively at repetitive sequences.
Department of Pathology, Gittlen Cancer Research Foundation, Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA 17033, USA.
Suzanne E
SE
Hile
Xiaoxiao
X
Wang
Marietta Y W T
MY
Lee
Kristin A
KA
Eckert
D000483:Alleles; D004247:DNA / Q000096:biosynthesis; D004249:DNA Damage; D004258:DNA Polymerase III / Q000378:metabolism; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism*; D006801:Humans; D054643:INDEL Mutation; D053842:Microsatellite Instability; D018895:Microsatellite Repeats; D000099270:Y-Family DNA Polymerases
D004247:DNA; D004258:DNA Polymerase III; D004259:DNA-Directed DNA Polymerase; C404302:POLK protein, human; D000099270:Y-Family DNA Polymerases; C112338:Rad30 protein