ABSTRACT
5-Methyl-2'-deoxycytidine (mC) and the product of its controlled oxidation, 5-hydroxymethyl-2'-cytidine (hmC), play a key role in the epigenetic regulation of gene expression, the cell differentiation, and the carcinogenesis. Due to spontaneious deamination, genomic CpG sites containing mC and hmC serve as mutagenesis hotspots. In addition, error-prone translesion and reparative DNA polymerases may serve as additional source of mutations in the lesion-containing regions with CpG sites. In the present work, we performed in vitro analysis of the accuracy of nucleotide incorporation opposite to mC and hmC by human DNA polymerases Polß, Polλ, Polη, Polι, PoIκ and primase polymerase PrimPol. The results of the study show a high accuracy of copying mC and hmC by the reparative DNA polymerases polymerases Polß and Polλ, while Polη, Polι, PoIκ, and PrimPol copied mC and hmC with less accuracy evident by incorporation of dAMP and dTMP. The same spectrum of error-prone dNMP incorporation was also noted at sites with unmodified cytosines.
Subject(s)
DNA-Directed DNA Polymerase , Epigenesis, Genetic , DNA Primase , DNA-Directed DNA Polymerase/genetics , DNA-Directed DNA Polymerase/metabolism , Deoxycytidine/analogs & derivatives , Humans , Multifunctional EnzymesABSTRACT
Many chemotherapy drugs block tumor cell division by damaging DNA. DNA polymerases eta (Pol η), iota (Pol ι), kappa (Pol κ), REV1 of the Y-family and zeta (Pol ζ) of the B-family efficiently incorporate nucleotides opposite a number of DNA lesions during translesion DNA synthesis. Primase-polymerase PrimPol and the Pol α-primase complex reinitiate DNA synthesis downstream of the damaged sites using their DNA primase activity. These enzymes can decrease the efficacy of chemotherapy drugs, contribute to the survival of tumor cells and to the progression of malignant diseases. DNA polymerases are promising targets for increasing the effectiveness of chemotherapy, and mutations and polymorphisms in some DNA polymerases can serve as additional prognostic markers in a number of oncological disorders.
Subject(s)
Antineoplastic Agents/pharmacology , DNA-Directed DNA Polymerase/metabolism , DNA/metabolism , Drug Resistance, Neoplasm , Nucleic Acid Synthesis Inhibitors/pharmacology , Protein Biosynthesis/drug effects , Animals , Antineoplastic Agents/therapeutic use , DNA Damage/drug effects , DNA Repair/drug effects , DNA Replication/drug effects , DNA-Directed DNA Polymerase/genetics , Humans , Neoplasms/drug therapy , Nucleic Acid Synthesis Inhibitors/therapeutic use , Polymorphism, GeneticABSTRACT
Tens of thousands of DNA lesions are formed in mammalian cells each day. DNA translesion synthesis is the main mechanism of cell defense against unrepaired DNA lesions. DNA polymerases iota (Pol ι), eta (Pol η), kappa (Pol κ), and zeta (Pol ζ) have active sites that are less stringent toward the DNA template structure and efficiently incorporate nucleotides opposite DNA lesions. However, these polymerases display low accuracy of DNA synthesis and can introduce mutations in genomic DNA. Impaired functioning of these enzymes can lead to an increased risk of cancer.