title: DNA sequence context greatly affects the accuracy of bypass across an ultraviolet light 6-4 photoproduct in mammalian cells.
abstract: Translesion DNA synthesis (TLS) is a DNA damage tolerance mechanism carried out by low-fidelity DNA polymerases that bypass DNA lesions, which overcomes replication stalling. Despite the miscoding nature of most common DNA lesions, several of them are bypassed in mammalian cells in a relatively accurate manner, which plays a key role maintaining a low mutation load. Whereas it is generally agreed that TLS across the major UV and sunlight induced DNA lesion, the cyclobutane pyrimidine dimer (CPD), is accurate, there were conflicting reports on whether the same is true for the thymine-thymine pyrimidine-pyrimidone(6-4) ultraviolet light photoproduct (TT6-4PP), which represents the second most common class of UV lesions. Using a TLS assay system based on gapped plasmids carrying site-specific TT6-4PP lesions in defined sequence contexts we show that the DNA sequence context markedly affected both the extent and accuracy of TLS. The sequence exhibiting higher TLS exhibited also higher error-frequency, caused primarily by semi-targeted mutations, at the nearest nucleotides flanking the lesion. Our results resolve the discrepancy reported on TLS across TT6-4PP, and suggest that TLS is more accurate in human cells than in mouse cells.
authors: Department of Biological Chemistry, Weizmann Institute of Science, Rehovot, 76100, Israel.
authors: Pola
authors: P
authors: Shriber
authors: Department of Biological Chemistry, Weizmann Institute of Science, Rehovot, 76100, Israel.
authors: Yael
authors: Y
authors: Leitner-Dagan
authors: Chemistry Department, New York University, NY 10003-5180, USA.
authors: Nicholas
authors: N
authors: Geacintov
authors: Department of Biological Chemistry, Weizmann Institute of Science, Rehovot, 76100, Israel. Electronic address: tamar.paz-elizur@weizmann.ac.il.
authors: Tamar
authors: T
authors: Paz-Elizur
authors: Department of Biological Chemistry, Weizmann Institute of Science, Rehovot, 76100, Israel. Electronic address: zvi.livneh@weizmann.ac.il.
authors: Zvi
authors: Z
authors: Livneh
mesh_terms: D000818:Animals; D002461:Cell Line, Transformed; D004249:DNA Damage; D006801:Humans; D051379:Mice; D009154:Mutation; D011740:Pyrimidine Dimers / Q000235:genetics / Q000378:metabolism*; D013045:Species Specificity; D014466:Ultraviolet Rays / Q000009:adverse effects*
chemical_list: D011740:Pyrimidine Dimers
keywords: DNA damage; DNA repair; Error-prone repair; Lesion bypass; UV mutagenesis