Requirement for PCNA in DNA Mismatch Repair at a Step Preceding DNA Resynthesis

Umar, Asad; Buermeyer, Andrew B.; Simon, John; Thomas, David C.; Clark, Allan; Liskay, R. Michael; Kunkel, Thomas A.

doi:10.1016/s0092-8674(00)81323-9

Cited by 530 publications

(461 citation statements)

References 47 publications

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“…Later, in vitro reconstitution of human MMR with purified proteins revealed the additional requirements for the sliding clamp PCNA and its loader RFC for 3′ directed MMR [6]. This finding coincided with an earlier report that PCNA was required for MMR prior to replacement strand synthesis [7]. The possibility of a cryptic 3′ → 5′ hydrolytic activity in ExoI was raised [6], but no evidence was found.…”

supporting

confidence: 64%

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Human MutLα: The jack of all trades in MMR is also an endonuclease

Yang

2007

DNA Repair

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SummaryRecently, Paul Modrich's group reported the discovery of an intrinsic endonuclease activity for human MutLα. This breakthrough provides a satisfactory answer to the longstanding puzzle of a missing nuclease activity in human mismatch repair and will undoubtedly lead to new investigations of DNA repair and replication. Here, the implications of this exciting new finding are discussed in the context of mismatch repair in E. coli and humans.Correction of replication errors by mismatch repair (MMR) has long been recognized as critical for genomic stability. Inactivation of MMR in humans has been implicated in > 90% of hereditary nonpolyposis colorectal cancers [1]. Like every DNA repair process, the success of MMR depends on two essential steps: lesion detection and removal. MMR is unique in two aspects. The targets of repair are normal rather than damaged nucleotides, and nucleotide removal has to be specific to the newly synthesized daughter strand and not the template. E. coli MMR is the best understood and has been fully reconstituted in vitro using a dozen or so purified proteins [2,3]. Recognition of a normal nucleotide that fails to make a Watson-Crick base pair in a DNA duplex is accomplished by the MutS protein. The strand specificity of MMR in E. coli is conferred by a sequence and methylation specific endonuclease MutH, which makes an incision (nick) 5′ to a GATC sequence in the unmethylated daughter strand. The GATC sequence may be several hundred base pairs from the mismatch on either the 5′ or 3′ side (Fig. 1A). The direction of daughter strand removal is strongly biased towards the shorter track between the nick and mismatch in a circular genome. The degradation of hundreds to a thousand nucleotides is carried out by one of several exonucleases with 5′ → 3′ or 3′-gt; 5′ polarity in the presence of the UvrD helicase and the single strand binding protein SSB. An additional central player in MMR is MutL, a molecular matchmaker that mediates proteinprotein interactions and coordinates mismatch recognition with strand incision and degradation (Fig. 1A).The MMR pathway is conserved from E. coli to humans [3]. The essential proteins known to specialize in human MMR are so far limited to MutS and MutL homologs and a 5′ → 3′ exonuclease, ExoI. Eukaryotic MutS and MutL are heterodimers of homologous subunits as opposed to homodimers in bacteria. Human MutSα consists of MSH2 and MSH6, and MutLα consists of MLH1 and PMS2. A strand-specific endonuclease that nicks the daughter strand, like MutH in E. coli, is missing in all eukaryotes and in many bacteria. It is thusCorrespondence and request for material should be addressed to W.Y. e-mail: Wei.Yang@nih.gov phone: (301), 402-4645, fax: (301) 496-0201. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its...

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supporting

confidence: 64%

“…How does MMR compete with other DNA repair pathways? Kadyrov et al suggest that it is the dual interaction of PCNA with both MutSα and MutLα [7,30,32,33] that may activate MMR. It will be of great interest to get to the bottom of the molecular interactions and their roles in genome stability.…”

mentioning

confidence: 99%

Human MutLα: The jack of all trades in MMR is also an endonuclease

Yang

2007

DNA Repair

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“…Reduced levels of p21 might be expected to increase the likelihood of apoptosis by forcing G1 cells into S-phase prematurely, causing conversion of singlestrand DNA breaks into double-strand breaks. However, recent studies suggest that p21 may also function to inhibit certain forms of DNA repair (Pan et al, 1995;Umar et al, 1996) and to induce apoptosis (Saeed Sheikh et al, 1995). Thus SF-induced decreases in p21 levels might contribute to its cytoprotective activity.…”

Section: Discussionmentioning

confidence: 99%

Scatter factor protects epithelial and carcinoma cells against apoptosis induced by DNA-damaging agents

et al. 1998

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“…PCNA is a highly conserved eukaryotic homotrimeric protein that assembles around DNA to form a sliding clamp and acts as a processivity factor for the replicative polymerase (reviewed in [16]). PCNA interacts with a large variety of proteins involved in DNA replication, lesion bypass, DNA repair, and cell cycle control, such as DNA polymerases δ and ε [17], DNA polymerase η [18], LIGI [19], MSH3 and MSH6 [20], FEN1 [21], GADD45 [22], and p21 [23]. An eight amino acid conserved motif (Q-x-x-[I/L/M]-x-x-F-[F/ Y]) in these proteins modulates their binding to PCNA [24].…”

Section: Introductionmentioning

confidence: 99%

Physical and functional interaction of human nuclear uracil-DNA glycosylase with proliferating cell nuclear antigen

Bennett

2005

DNA Repair

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Uracil residues arise in DNA by the misincorporation of dUMP in place of dTMP during DNA replication or by the deamination of cytosine in DNA. Uracil-DNA glycosylase initiates DNA base excision repair of uracil residues by catalyzing the hydrolysis of the N-glycosylic bond linking the uracil base to deoxyribose. In human cells, the nuclear form of uracil-DNA glycosylase (UNG2) contains a conserved PCNA-binding motif located at the N-terminus that has been implicated experimentally in binding PCNA. Here we use purified preparations of UNG2 and PCNA to demonstrate that UNG2 physically associates with PCNA. UNG2 co-eluted with PCNA during size exclusion chromatography and bound to a PCNA affinity column. Association of UNG2 with PCNA was abolished by the addition of 100 mM NaCl, and significantly decreased in the presence of 10 mM MgCl 2 . The functional significance of the UNG2·PCNA association was demonstrated by UNG2 activity assays. Addition of PCNA (30-810 pmol) to standard uracil-DNA glycosylase reactions containing linear [uracil-3 H]DNA stimulated UNG2 catalytic activity up to 2.6-fold. UNG2 activity was also stimulated by 7.5 mM MgCl 2 . The stimulatory effect of PCNA was increased by the addition of MgCl 2 ; however, the dependence on PCNA concentration was the same, indicating that the effects of MgCl 2 and PCNA on UNG2 activity occurred by independent mechanisms. Loading of PCNA onto the DNA substrate was required for stimulation, as the activity of UNG2 on circular DNA substrates was not affected by the addition of PCNA. Addition of replication factor C and ATP to reactions containing 90 pmol of PCNA resulted in two-fold stimulation of UNG2 activity on circular DNA.

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Requirement for PCNA in DNA Mismatch Repair at a Step Preceding DNA Resynthesis

Cited by 530 publications

References 47 publications

Human MutLα: The jack of all trades in MMR is also an endonuclease

Human MutLα: The jack of all trades in MMR is also an endonuclease

Scatter factor protects epithelial and carcinoma cells against apoptosis induced by DNA-damaging agents

Physical and functional interaction of human nuclear uracil-DNA glycosylase with proliferating cell nuclear antigen

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