title: Ribonucleotides misincorporated into DNA act as strand-discrimination signals in eukaryotic mismatch repair.
abstract: To improve replication fidelity, mismatch repair (MMR) must detect non-Watson-Crick base pairs and direct their repair to the nascent DNA strand. Eukaryotic MMR in vitro requires pre-existing strand discontinuities for initiation; consequently, it has been postulated that MMR in vivo initiates at Okazaki fragment termini in the lagging strand and at nicks generated in the leading strand by the mismatch-activated MLH1/PMS2 endonuclease. We now show that a single ribonucleotide in the vicinity of a mismatch can act as an initiation site for MMR in human cell extracts and that MMR activation in this system is dependent on RNase H2. As loss of RNase H2 in S.cerevisiae results in a mild MMR defect that is reflected in increased mutagenesis, MMR in vivo might also initiate at RNase H2-generated nicks. We therefore propose that ribonucleotides misincoporated during DNA replication serve as physiological markers of the nascent DNA strand.
authors.affiliation: Institute of Molecular Cancer Research of the University of Zurich and ETH Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland.
authors.forename: Medini Manohar
authors.initials: MM
authors.lastname: Ghodgaonkar
authors.forename: Federico
authors.initials: F
authors.lastname: Lazzaro
authors.forename: Maite
authors.initials: M
authors.lastname: Olivera-Pimentel
authors.forename: Mariela
authors.initials: M
authors.lastname: Artola-Borán
authors.forename: Petr
authors.initials: P
authors.lastname: Cejka
authors.forename: Martin A
authors.initials: MA
authors.lastname: Reijns
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Jackson
authors.forename: Paolo
authors.initials: P
authors.lastname: Plevani
authors.forename: Marco
authors.initials: M
authors.lastname: Muzi-Falconi
authors.forename: Josef
authors.initials: J
authors.lastname: Jiricny
mesh_terms: D000818:Animals; D020137:Base Pair Mismatch; D002474:Cell-Free System; D002478:Cells, Cultured; D004247:DNA / Q000235:genetics* / Q000378:metabolism; D053843:DNA Mismatch Repair; D004260:DNA Repair; D004261:DNA Replication / Q000235:genetics*; D057809:HEK293 Cells; D006801:Humans; D051379:Mice; D016296:Mutagenesis / Q000235:genetics; D016914:Ribonuclease H / Q000235:genetics / Q000378:metabolism; D012265:Ribonucleotides / Q000235:genetics* / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism
chemical_list: C022262:Okazaki fragments; D012265:Ribonucleotides; D004247:DNA; C091139:ribonuclease HII; D016914:Ribonuclease H