scholarly journals MSH2–MSH6 stimulates DNA polymerase η, suggesting a role for A:T mutations in antibody genes

2005 ◽  
Vol 201 (4) ◽  
pp. 637-645 ◽  
Author(s):  
Teresa M. Wilson ◽  
Alexandra Vaisman ◽  
Stella A. Martomo ◽  
Patsa Sullivan ◽  
Li Lan ◽  
...  
Keyword(s):  
Dna Polymerase ◽  
Base Excision Repair ◽  
Somatic Hypermutation ◽  
Excision Repair ◽  
Cytidine Deaminase ◽  
Abasic Site ◽  
Cell Extracts ◽  
Activation Induced Cytidine Deaminase ◽  
Base Excision

Activation-induced cytidine deaminase deaminates cytosine to uracil (dU) in DNA, which leads to mutations at C:G basepairs in immunoglobulin genes during somatic hypermutation. The mechanism that generates mutations at A:T basepairs, however, remains unclear. It appears to require the MSH2–MSH6 mismatch repair heterodimer and DNA polymerase (pol) η, as mutations of A:T are decreased in mice and humans lacking these proteins. Here, we demonstrate that these proteins interact physically and functionally. First, we show that MSH2–MSH6 binds to a U:G mismatch but not to other DNA intermediates produced during base excision repair of dUs, including an abasic site and a deoxyribose phosphate group. Second, MSH2 binds to pol η in solution, and endogenous MSH2 associates with the pol in cell extracts. Third, MSH2–MSH6 stimulates the catalytic activity of pol η in vitro. These observations suggest that the interaction between MSH2–MSH6 and DNA pol η stimulates synthesis of mutations at bases located downstream of the initial dU lesion, including A:T pairs.

scholarly journals HECTD1 promotes base excision repair in nucleosomes through chromatin remodelling

2019 ◽  
Vol 48 (3) ◽  
pp. 1301-1313 ◽  
Author(s):  
Laura Bennett ◽  
Eleanor C E T Madders ◽  
Jason L Parsons
Keyword(s):  
Dna Damage ◽  
Base Excision Repair ◽  
Genome Stability ◽  
Excision Repair ◽  
Chromatin Remodelling ◽  
Abasic Site ◽  
Cell Extracts ◽  
Base Excision ◽  
Cellular Dna

Abstract Base excision repair (BER) is the major cellular DNA repair pathway that recognises and excises damaged DNA bases to help maintain genome stability. Whilst the major enzymes and mechanisms co-ordinating BER are well known, the process of BER in chromatin where DNA is compacted with histones, remains unclear. Using reconstituted mononucleosomes containing a site-specific synthetic abasic site (tetrahydrofuran, THF), we demonstrate that the DNA damage is less efficiently incised by recombinant AP endonuclease 1 (APE1) when the DNA backbone is facing the histone core (THF-in) compared to that orientated away (THF-out). However, when utilizing HeLa whole cell extracts, the difference in incision of THF-in versus THF-out is less pronounced suggesting the presence of chromatin remodelling factors that stimulate THF accessibility to APE1. We subsequently purified an activity from HeLa cell extracts and identify this as the E3 ubiquitin ligase, HECTD1. We demonstrate that a recombinant truncated form of HECTD1 can stimulate incision of THF-in by APE1 in vitro by histone ubiquitylation, and that siRNA-mediated depletion of HECTD1 leads to deficiencies in DNA damage repair and decreased cell survival following x-ray irradiation, particularly in normal fibroblasts. Thus, we have now identified HECTD1 as an important factor in promoting BER in chromatin.

In Vitro Base Excision Repair Assay Using Mammalian Cell Extracts

1999 ◽  
pp. 301-315 ◽  
Author(s):  
Guido Frosina ◽  
Enrico Cappelli ◽  
Paola Fortini ◽  
Eugenia Dogliotti
Keyword(s):  
Mammalian Cell ◽  
Base Excision Repair ◽  
Excision Repair ◽  
Cell Extracts ◽  
Base Excision

scholarly journals DNA polymerase X from Deinococcus radiodurans implicated in bacterial tolerance to DNA damage is characterized as a short patch base excision repair polymerase

Microbiology ◽  
2009 ◽  
Vol 155 (9) ◽  
pp. 3005-3014 ◽  
Author(s):  
Nivedita P. Khairnar ◽  
Hari S. Misra
Keyword(s):  
Dna Damage ◽  
Dna Polymerase ◽  
Base Excision Repair ◽  
Deinococcus Radiodurans ◽  
Excision Repair ◽  
Strand Break ◽  
Klenow Fragment ◽  
E Coli ◽  
Base Excision

The Deinococcus radiodurans R1 genome encodes an X-family DNA repair polymerase homologous to eukaryotic DNA polymerase β. The recombinant deinococcal polymerase X (PolX) purified from transgenic Escherichia coli showed deoxynucleotidyltransferase activity. Unlike the Klenow fragment of E. coli, this enzyme showed short patch DNA synthesis activity on heteropolymeric DNA substrate. The recombinant enzyme showed 5′-deoxyribose phosphate (5′-dRP) lyase activity and base excision repair function in vitro, with the help of externally supplied glycosylase and AP endonuclease functions. A polX disruption mutant of D. radiodurans expressing 5′-dRP lyase and a truncated polymerase domain was comparatively less sensitive to γ-radiation than a polX deletion mutant. Both mutants showed higher sensitivity to hydrogen peroxide. Excision repair mutants of E. coli expressing this polymerase showed functional complementation of UV sensitivity. These results suggest the involvement of deinococcal polymerase X in DNA-damage tolerance of D. radiodurans, possibly by contributing to DNA double-strand break repair and base excision repair.

In Vitro Base Excision Repair Assay Using Mammalian Cell Extracts

2003 ◽  
pp. 301-315 ◽  
Author(s):  
Guido Frosina ◽  
Enrico Cappelli ◽  
Paola Fortini ◽  
Eugenia Dogliotti
Keyword(s):  
Mammalian Cell ◽  
Base Excision Repair ◽  
Excision Repair ◽  
Cell Extracts ◽  
Base Excision

scholarly journals DNA polymerase β prevents AID-instigated mutagenic non-canonical mismatch DNA repair

2020 ◽  
Author(s):  
Mahnoush Bahjat ◽  
Maria Stratigopoulou ◽  
Bas Pilzecker ◽  
Tijmen P. van Dam ◽  
Simon Mobach ◽  
...  
Keyword(s):  
B Cells ◽  
Dna Polymerase ◽  
Somatic Hypermutation ◽  
Excision Repair ◽  
Clonal Selection ◽  
Cytidine Deaminase ◽  
Affinity Maturation ◽  
Dna Polymerase Β ◽  
Immunoglobulin Variable Genes ◽  
Base Excision

ABSTRACTIn B cells, the error-prone repair of activation-induced cytidine deaminase (AID)-induced lesions in immunoglobulin variable genes cause somatic hypermutation (SHM) of antibody genes. Due to clonal selection in the germinal centers (GC) this active mutation process provides the molecular basis for antibody affinity maturation. AID deaminates cytosine (C) to create uracil (U) in DNA. Typically, the short patch base excision repair (spBER) effectively restores genomic U lesions. We here demonstrate that GC B cells actively degrade DNA polymerase β (Polβ), resulting in the inactivation of the gap-filling step of spBER. Consequently, lesions instigated by AID, and likely other base damages, are channeled towards mutagenic non-canonical mismatch repair (mncMMR), responsible for the vast majority of mutations at adenine and thymine (A:T) bases. Apparently, GC B cells prohibit faithful spBER, thereby favoring A:T mutagenesis during SHM. Lastly, our data suggest that the loss of Polβ relates to hypoxia that characterizes the GC microenvironment.

scholarly journals Base excision repair of adenine/8-oxoguanine mispairs by an aphidicolin-sensitive DNA polymerase in human cell extracts

Oncogene ◽  
2002 ◽  
Vol 21 (34) ◽  
pp. 5204-5212 ◽  
Author(s):  
Eleonora Parlanti ◽  
Paola Fortini ◽  
Peter Macpherson ◽  
Jacques Laval ◽  
Eugenia Dogliotti
Keyword(s):  
Dna Polymerase ◽  
Base Excision Repair ◽  
Human Cell ◽  
Excision Repair ◽  
Cell Extracts ◽  
Base Excision

In Vitro Base Excision Repair Assay Using Mammalian Cell Extracts

2008 ◽  
pp. 377-396 ◽  
Author(s):  
Guido Frosina ◽  
Enrico Cappelli ◽  
Monica Ropolo ◽  
Paola Fortini ◽  
Barbara Pascucci ◽  
...  
Keyword(s):  
Mammalian Cell ◽  
Base Excision Repair ◽  
Excision Repair ◽  
Cell Extracts ◽  
Base Excision
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