title: Human DNA polymerase ε is able to efficiently extend from multiple consecutive ribonucleotides.
abstract: Replicative DNA polymerases (Pols) help to maintain the high fidelity of replication in large part through their strong selectivity against mispaired deoxyribonucleotides. It has recently been demonstrated that several replicative Pols from yeast have surprisingly low selectivity for deoxyribonucleotides over their analogous ribonucleotides. In human cells, ribonucleotides are found in great abundance over deoxyribonucleotides, raising the possibility that ribonucleotides are incorporated in the human genome at significant levels during normal cellular functions. To address this possibility, the ability of human DNA polymerase ε to incorporate ribonucleotides was tested. At physiological concentrations of nucleotides, human Pol ε readily inserts and extends from incorporated ribonucleotides. Almost half of inserted ribonucleotides escape proofreading by 3' → 5' exonuclease-proficient Pol ε, indicating that ribonucleotide incorporation by Pol ε is likely a significant event in human cells. Human Pol ε is also efficient at extending from primers terminating in up to five consecutive ribonucleotides. This efficient extension appears to result from reduced exonuclease activity on primers containing consecutive 3'-terminal ribonucleotides. These biochemical properties suggest that Pol ε is a likely source of ribonucleotides in human genomic DNA.
authors.affiliation: Department of Biochemistry and Molecular Biology and the Tulane Cancer Center, Tulane University School of Medicine, New Orleans, Louisiana 70112, USA.
authors.forename: A Yasemin
authors.initials: AY
authors.lastname: Göksenin
authors.forename: Walter
authors.initials: W
authors.lastname: Zahurancik
authors.forename: Kimberly G
authors.initials: KG
authors.lastname: LeCompte
authors.forename: David J
authors.initials: DJ
authors.lastname: Taggart
authors.forename: Zucai
authors.initials: Z
authors.lastname: Suo
authors.forename: Zachary F
authors.initials: ZF
authors.lastname: Pursell
mesh_terms: D003570:Cytidine Triphosphate / Q000378:metabolism; D004247:DNA / Q000096:biosynthesis; D004257:DNA Polymerase II / Q000378:metabolism*; D005092:Exonucleases / Q000378:metabolism; D006801:Humans; D000075223:Poly-ADP-Ribose Binding Proteins; D012265:Ribonucleotides / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D000075223:Poly-ADP-Ribose Binding Proteins; D012265:Ribonucleotides; D003570:Cytidine Triphosphate; D004247:DNA; D004257:DNA Polymerase II; C119525:POLE protein, human; D005092:Exonucleases