Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.30.2 (endonuclease)
 18,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Genetic and biochemical studies have indicated that mismatch repair proteins can interact with recombination intermediates. In this study, gel shift assays and electron microscopic analysis were used to show that the Saccharomyces cerevisiae MSH2/6 complex binds to Holliday junctions and has an affinity and specificity for them that is at least as high as it has as for mispaired bases. Under equilibrium binding conditions, the MSH2/6 complex had a Kd of binding to Holliday junctions of 0.5 nM. The MSH2/6 complex enhanced the cleavage of Holliday junctions by T4 endonuclease VII and T7 endonuclease I. This is consistent with the view that the MSH2/6 complex can function in both mismatch repair and the resolution of recombination intermediates as predicted by genetic studies.
 ...
PMID:'Saccharomyces cerevisiae MSH2/6 complex interacts with Holliday junctions and facilitates their cleavage by phage resolution enzymes. 1006 81

The instability of simple tandem repeats, such as human minisatellite loci, has been suggested to arise by gene conversions. In Saccharomyces cerevisiae, a double-strand break (DSB) was created by the HO endonuclease so that DNA polymerases associated with gap repair must traverse an artificial minisatellite of perfect 36-bp repeats or a yeast Y' minisatellite containing diverged 36-bp repeats. Gene conversions are frequently accompanied by changes in repeat number when the template contains perfect repeats. When the ends of the DSB have nonhomologous tails of 47 and 70 nucleotides that must be removed before repair DNA synthesis can begin, 16% of gene conversions had rearrangements, most of which were contractions, almost always in the recipient locus. When efficient removal of nonhomologous tails was prevented in rad1 and msh2 strains, repair was reduced 10-fold, but among survivors there was a 10-fold reduction in contractions. Half the remaining events were expansions. A similar decrease in the contraction rate was observed when the template was modified so that DSB ends were homologous to the template; and here, too, half of the remaining rearrangements were expansions. In this case, efficient repair does not require RAD1 and MSH2, consistent with our previous observations. In addition, without nonhomologous DSB ends, msh2 and rad1 mutations did not affect the frequency or the distribution of rearrangements. We conclude that the presence of nonhomologous ends alters the mechanism of DSB repair, likely through early recruitment of repair proteins including Msh2p and Rad1p, resulting in more frequent contractions of repeated sequences.
 ...
PMID:Expansions and contractions in 36-bp minisatellites by gene conversion in yeast. 1133 26

Unpaired and mispaired bases in DNA can arise by replication errors, spontaneous or induced base modifications, and during recombination. The major pathway for correction of mismatches arising during replication is the MutHLS pathway of Escherichia coli and related pathways in other organisms. MutS initiates repair by binding to the mismatch, and activates together with MutL the MutH endonuclease, which incises at hemimethylated dam sites and thereby mediates strand discrimination. Multiple MutS and MutL homologues exist in eukaryotes, which play different roles in the mismatch repair (MMR) pathway or in recombination. No MutH homologues have been identified in eukaryotes, suggesting that strand discrimination is different to E. coli. Repair can be initiated by the heterodimers MSH2-MSH6 (MutSalpha) and MSH2-MSH3 (MutSbeta). Interestingly, MSH3 (and thus MutSbeta) is missing in some genomes, as for example in Drosophila, or is present as in Schizosaccharomyces pombe but appears to play no role in MMR. MLH1-PMS1 (MutLalpha) is the major MutL homologous heterodimer. Again some, but not all, eukaryotes have additional MutL homologues, which all form a heterodimer with MLH1 and which play a minor role in MMR. Additional factors with a possible function in eukaryotic MMR are PCNA, EXO1, and the DNA polymerases delta and epsilon. MMR-independent pathways or factors that can process some types of mismatches in DNA are nucleotide-excision repair (NER), some base excision repair (BER) glycosylases, and the flap endonuclease FEN-1. A pathway has been identified in Saccharomyces cerevisiae and human that corrects loops with about 16 to several hundreds of unpaired nucleotides. Such large loops cannot be processed by MMR.
 ...
PMID:DNA mismatch repair and mutation avoidance pathways. 1192 Jun 79

In the budding yeast Saccharomyces cerevisiae, null alleles of several DNA repair and recombination genes confer defects in recombination that grow more severe with decreasing sequence length, indicating that they are required for short-sequence recombination (SSR). RAD1 and RAD10, which encode the subunits of the structure-specific endonuclease Rad1/10, are critical for SSR. MRE11, RAD50, and XRS2, which encode the subunits of M/R/X, another complex with nuclease activity, are also crucially important. Genetic evidence suggests that Rad1/10 and M/R/X act on the same class of substrates during SSR. MSH2 and MSH3, which encode subunits of Msh2/3, a complex active during mismatch repair and recombination, are also important for SSR but play a more restricted role. Additional evidence suggests that SSR is distinct from nonhomologous end joining and is superimposed upon basal homologous recombination.
 ...
PMID:Multiple pathways promote short-sequence recombination in Saccharomyces cerevisiae. 1210 Dec 30

Bulky DNA lesions are mainly repaired by nucleotide excision repair (NER), in which the interaction of ERCC1 with XPA protein recruits the ERCC1-XPF complex, which acts as a structure-specific endonuclease in the repair process. However, additional functions besides NER have been suggested for the ERCC1-XPF complex, because ERCC1- or XPF-deficient rodent cells are significantly more sensitive to DNA interstrand cross-linking (ICL) agents such as cis-diamminedichloroplatinum(II) (CDDP) than any other NER-deficient cells and because ERCC1-deficient mice suffer a more severe phenotype than XPA-deficient mice. By using RNA interference we show here that suppression of ERCC1 expression increases the sensitivity of xeroderma pigmentosum group A (XPA)-deficient human cells to CDDP but not to UV. This increased sensitivity to CDDP is observed in mouse cells defective in Xpa as well but not in cells defective both in Xpa and the mismatch repair gene Msh2. These data suggest that ERCC1 and MSH2 are involved co-operatively in CDDP resistance in mammalian cells. As a possible molecular basis, we show further a physical interaction between endogenous ERCC1 and MSH2 complexes in HeLa cell extracts. Using tagged ERCC1 in COS7 cells, the minimum region in ERCC1 necessary for the immuno-precipitation of MSH2 is turned out to be the carboxyl-terminal domain between the 184th and 260th amino acid, which is partly overlapping with the XPF-binding domain of ERCC1. This interaction may be important in additional functions of ERCC1-XPF including the repair of CDDP-induced DNA damage.
 ...
PMID:Functional and physical interactions between ERCC1 and MSH2 complexes for resistance to cis-diamminedichloroplatinum(II) in mammalian cells. 1470 47

Recombination between moderately divergent DNA sequences is impaired compared with identical sequences. In yeast, an HO endonuclease-induced double-strand break can be repaired by single-strand annealing (SSA) between flanking homologous sequences. A 3% sequence divergence between 205-bp sequences flanking the double-strand break caused a 6-fold reduction in repair compared with identical sequences. This reduction in heteroduplex rejection was suppressed in a mismatch repair-defective msh6 Delta strain and partially suppressed in an msh2 separation-of-function mutant. In mlh1 Delta strains, heteroduplex rejection was greater than in msh6 Delta strains but less than in wild type. Deleting PMS1, MLH2,or MLH3 had no effect on heteroduplex rejection, but a pms1 Delta mlh2 Delta mlh3 Delta triple mutant resembled mlh1 Delta. However, correction of the mismatches within heteroduplex SSA intermediates required PMS1 and MLH1 to the same extent as MSH2 and MSH6. An SSA competition assay in which either diverged or identical repeats can be used for repair showed that heteroduplex DNA is likely to be unwound rather than degraded. This conclusion is supported by the finding that deleting the SGS1 helicase also suppressed heteroduplex rejection.
 ...
PMID:Heteroduplex rejection during single-strand annealing requires Sgs1 helicase and mismatch repair proteins Msh2 and Msh6 but not Pms1. 1519 78

The multifunctional mammalian apurinic/apyrimidinic (AP) endonuclease (APE) participates in the repair of AP sites in the cellular DNA as well as participating in the redox regulation of the transcription factor function. The function of APE is considered as the rate-limiting step in DNA base excision repair. Paradoxically, an unbalanced increase in APE protein leads to genetic instability. Therefore, we investigated the mechanisms of genetic instability that are induced by APE. Here, we report that the overexpression of APE protein disrupts the repair of DNA mismatches, which results in microsatellite instability (MSI). We found that expression of APE protein led to the suppression of the repair of DNA mismatches in the normal human fibroblast cells. Western blot analysis revealed that hMSH6 protein was markedly reduced in the APE-expressing cells. Moreover, the addition of purified Mutalpha (MSH2 and MSH6 complex) to the extracts from the APE-expressing cells led to the restoration of mismatch repair (MMR) activity. By performing MMR activity assay and MSI analysis, we found that the co-expression of hMSH6 and APE exhibited the microsatellite stability, whereas the expression of APE alone generated the MSI-high phenotype. The APE-mediated decrease in MMR activity described here demonstrates the presence of a new and highly effective APE-mediated mechanism for MSI.
 ...
PMID:Human AP endonuclease suppresses DNA mismatch repair activity leading to microsatellite instability. 1614 91

We have previously shown that recombination between 400-bp substrates containing only 4-bp differences, when present in an inverted repeat orientation, is suppressed by >20-fold in wild-type strains of S. cerevisiae. Among the genes involved in this suppression were three genes involved in mismatch repair--MSH2, MSH3, and MSH6--and one in nucleotide excision repair, RAD1. We now report the involvement of these genes in interchromosomal recombination occurring via crossovers using these same short substrates. In these experiments, recombination was stimulated by a double-strand break generated by the HO endonuclease and can occur between completely identical (homologous) substrates or between nonidentical (homeologous) substrates. In addition, a unique feature of this system is that recombining DNA strands can be given a choice of either type of substrate. We find that interchromosomal crossover recombination with these short substrates is severely inhibited in the absence of MSH2, MSH3, or RAD1 and is relatively insensitive to the presence of mismatches. We propose that crossover recombination with these short substrates requires the products of MSH2, MSH3, and RAD1 and that these proteins have functions in recombination in addition to the removal of terminal nonhomology. We further propose that the observed insensitivity to homeology is a result of the difference in recombinational mechanism and/or the timing of the observed recombination events. These results are in contrast with those obtained using longer substrates and may be particularly relevant to recombination events between the abundant short repeated sequences that characterize the genomes of higher eukaryotes.
 ...
PMID:The effects of mismatch repair and RAD1 genes on interchromosomal crossover recombination in Saccharomyces cerevisiae. 1658 36

We experimented a novel reporter system to analyze intrachromosomal recombination between homeologous sequences in Arabidopsis germ cell lineages. The recombination substrates used are the BAR and PAT genes which diverge by about 13% at the nucleotide level and confer resistance to the herbicide glufosinate. DNA double-strand breaks (DSBs) were generated by the I-Sce1 endonuclease to induce recombination. Loss of AtMSH2 induces a 3-fold increase of the frequency of recombination events indicating that AtMSH2 is involved in the anti-recombination activity that prevents exchange between highly diverged sequences in Arabidopsis. Molecular analysis of recombined alleles indicates that in wild type plants the single strand annealing (SSA) pathway can process more efficiently homologous 3' ends than 3' ends generated by resection of non-homologous overhangs. The loss of AtMSH2 disturbs this process, leading to a modification of the distribution of the BAR/PAT junctions and therefore showing that the MSH2 function is also involved in determining the structure of the recombined alleles. In addition, conversion tracts were observed in some alleles. They are shorter in MSH2 deficient plants than in wild-type, suggesting that a short-patch mismatch repair, not controlled by MSH2, could exist in Arabidopsis.
 ...
PMID:Impact of the loss of AtMSH2 on double-strand break-induced recombination between highly diverged homeologous sequences in Arabidopsis thaliana germinal tissues. 1729 56

DNA interstrand cross-linking agents have been widely used in chemotherapeutic treatment of cancer. The majority of interstrand cross-links (ICLs) in mammalian cells are removed via a complex process that involves the formation of double-strand breaks at replication forks, incision of the ICL, and subsequent error-free repair by homologous recombination. How double-strand breaks effect the removal of ICLs and the downstream homologous recombination process is not clear. Here, we describe a plasmid-based recombination assay in which one copy of the CFP gene is inactivated by a site-specific psoralen ICL and can be repaired by gene conversion with a mutated homologous donor sequence. We found that the homology-dependent recombination (HDR) is inhibited by the ICL. However, when we introduced a double-strand break adjacent to the site of the ICL, the removal of the ICL was enhanced and the substrate was funneled into a HDR repair pathway. This process was not dependent on the nucleotide excision repair pathway, but did require the ERCC1-XPF endonuclease and REV3. In addition, both the Fanconi anemia pathway and the mismatch repair protein MSH2 were required for the recombinational repair processing of the ICL. These results suggest that the juxtaposition of an ICL and a DSB stimulates repair of ICLs through a process requiring components of mismatch repair, ERCC1-XPF, REV3, Fanconi anemia proteins, and homologous recombination repair factors.
 ...
PMID:Double-strand breaks induce homologous recombinational repair of interstrand cross-links via cooperation of MSH2, ERCC1-XPF, REV3, and the Fanconi anemia pathway. 1766 95


1 2 Next >>