Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.4.1 (phosphodiesterase)
 18,767 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Werner syndrome is a human disorder characterized by premature aging, genomic instability, and abnormal telomere metabolism. The Werner syndrome protein (WRN) is the only known member of the RecQ DNA helicase family that contains a 3' --> 5'-exonuclease. However, it is not known whether both activities coordinate in a biological pathway. Here, we describe DNA structures, forked duplexes containing telomeric repeats, that are substrates for the simultaneous action of both WRN activities. We used these substrates to study the interactions between the WRN helicase and exonuclease on a single DNA molecule. WRN helicase unwinds at the forked end of the substrate, whereas the WRN exonuclease acts at the blunt end. Progression of the WRN exonuclease is inhibited by the action of WRN helicase converting duplex DNA to single strand DNA on forks of various duplex lengths. The WRN helicase and exonuclease act in concert to remove a DNA strand from a long forked duplex that is not completely unwound by the helicase. We analyzed the simultaneous action of WRN activities on the long forked duplex in the presence of the WRN protein partners, replication protein A (RPA), and the Ku70/80 heterodimer. RPA stimulated the WRN helicase, whereas Ku stimulated the WRN exonuclease. In the presence of both RPA and Ku, the WRN helicase activity dominated the exonuclease activity.
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PMID:Coordinate action of the helicase and 3' to 5' exonuclease of Werner syndrome protein. 1157 72

Werner syndrome (WS) is a premature aging syndrome caused by mutations in the WS gene (WRN) and a deficiency in the function of the Werner protein (WRN). WRN is a multifunctional nuclear protein that catalyzes three DNA-dependent reactions: a 3'-5'-exonuclease, an ATPase, and a 3'-5'-helicase. Deficiency in WRN results in a cellular phenotype of genomic instability. The biochemical characteristics of WRN and the cellular phenotype of WRN mutants suggest that WRN plays an important role in DNA metabolic pathways such as recombination, transcription, replication, and repair. The catalytic activities of WRN have been extensively studied and are fairly well understood. However, much less is known about the domain-specific interactions between WRN and its DNA substrates. This study identifies and characterizes three distinct WRN DNA binding domains using recombinant truncated fragments of WRN and five DNA substrates (long forked duplex, blunt-ended duplex, single-stranded DNA, 5'-overhang duplex, and Holliday junction). Substrate-specific DNA binding activity was detected in three domains, one N-terminal and two different C-terminal WRN fragments (RecQ conserved domain and helicase RNase D conserved domain-containing domains). The substrate specificity of each DNA binding domain may indicate that each protein domain has a distinct biological function. The importance of these results is discussed with respect to proposed roles for WRN in distinct DNA metabolic pathways.
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PMID:Werner syndrome protein contains three structure-specific DNA binding domains. 1453 20

Werner syndrome is a genetic disease characterized by early ageing, excess cancer risk, high incidence of type II diabetes mellitus, early atherosclerosis, ocular cataracts, and osteoporosis. The protein encoded by the defective gene, WRN (WRNp) associates with three activities, that is, a RecQ DNA helicase, 3'-5'-exonuclease and ATPase activities. By highlighting the DNA helicase activity, a widespread consensus in WS-associated defect(s) has been established, pointing toward a deficiency in maintaining DNA integrity. However, a possible involvement of redox pathways in WS may be suggested by several lines of evidence that include: (i) the multiple functions and interactions of WRNp with oxidative stress-related activities and factors; (ii) the pleiotropic WS clinical phenotype encompassing a number of oxidative stress-related pathologies; (iii) redox-related toxicity mechanisms of several xenobiotics exerting excess toxicity in WS cells; (iv) recent in vivo and in vitro findings of redox abnormalities in WS patients and in WS cells. The working hypothesis is raised that a deficiency in WRNp, and the pleiotropic clinical phenotype in WS patients may provide the basis to envision an underlying in vivo prooxidant state, which causes oxidative damage to biomolecules, with multiple oxidative stress-related alterations, resulting in multi-faceted clinical consequences.
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PMID:Multiple involvement of oxidative stress in Werner syndrome phenotype. 1633 57

Flap endonuclease-1 (FEN1) is a structure specific endonuclease. The natural substrates of FEN1 are 5'-flap structures formed by three DNA chains one of them has unannealed flapped 5'-end (flap). Flap structures are the intermediates of different processes of DNA metabolism, such as DNA recombination, Okazaki fragment maturation during replication of lagging strand, as well as strand displacement DNA synthesis in base excision repair. FEN1 also possesses 5'-exonuclease activity and newly discovered gap endonuclease activity. FEN1 is known to interact physically and functionally with a number of DNA replication and repair proteins such as the proliferating cell nuclear antigen, helicase/nuclease Dna2, WRN and BLM proteins, replication protein A, apurinic/apyrimidinic endonuclease 1, DNA polymerase beta, poly(ADP-riboso) polymerase 1, high mobility group protein 1, integrase of human immunodeficiency virus, transcription coactivator p300, chromatin proteins, cyclin-dependent kinases (Cdk1, Cdk2, Cyclin A). FEN1 activity is significant for maintaining the integrity of repeat sequences in genome. Recent data suppose the correlation between the abnormality of hFEN1 activity and arising/progression of neurodegenerative and cancer diseases. FEN1 has the dramatic effect on cell growth and development thereby attracting the interest to this enzyme.
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PMID:[Flap endonuclease-1 and its role in the processes of DNA metabolism in eucaryotic cells]. 1870 99

Even a partial loss of function of human RecQ helicase analogs causes adverse effects such as a cancer-prone Werner, Bloom or Rothmund-Thompson syndrome, whereas a complete RecQ deficiency in Escherichia coli is not deleterious for a cell. We show that this puzzling difference is due to different mechanisms of DNA double strand break (DSB) resection in E. coli and humans. Coupled helicase and RecA loading activities of RecBCD enzyme, which is found exclusively in bacteria, are shown to be responsible for channeling recombinogenic 3' ending tails toward productive, homologous and away from nonproductive, aberrant recombination events. On the other hand, in recB1080/recB1067 mutants, lacking RecBCD's RecA loading activity while preserving its helicase activity, DSB resection is mechanistically more alike that in eukaryotes (by its uncoupling from a recombinase polymerization step), and remarkably, the role of RecQ also becomes akin of its eukaryotic counterparts in a way of promoting homologous and suppressing illegitimate recombination. The sickly phenotype of recB1080 recQ mutant was further exacerbated by inactivation of an exonuclease I, which degrades the unwound 3' tail. The respective recB1080 recQ xonA mutant showed poor viability, DNA repair and homologous recombination deficiency, and very increased illegitimate recombination. These findings demonstrate that the metabolism of the 3' ending overhang is a decisive factor in tuning the balance of homologous and illegitimate recombination in E. coli, thus highlighting the importance of regulating DSB resection for preserving genome integrity. recB mutants used in this study, showing pronounced RecQ helicase and exonuclease I dependence, make up a suitable model system for studying mechanisms of DSB resection in bacteria. Also, these mutants might be useful for investigating functions of the conserved RecQ helicase family members, and congruently serve as a simpler, more defined model system for human oncogenesis.
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PMID:DNA end resection controls the balance between homologous and illegitimate recombination in Escherichia coli. 2272 24