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)

It was demonstrated previously that a deoxyribophosphodiesterase (dRpase) activity is associated with the DNA repair enzyme exonuclease I, and that this activity is stimulated by the addition of the E. coli single-stranded DNA-binding protein (Ssb). This activity catalyzes the release of deoxyribose-phosphate groups at apurinic/apyrimidinic (AP) sites in the DNA that have been cleared by the action of an AP endonuclease. We have now used the yeast two-hybrid system to demonstrate that a protein-protein interaction occurs between exonuclease I and Ssb. When the E. coli ssb gene was fused in frame to the DNA-activating domain of the GAL4 transcriptional activator and the exonuclease I gene was fused in frame to the DNA-binding domain, a functional GAL4 transcriptional activator was produced as determined by growth of yeast on selective medium and the measurement of beta-galactosidase activity. We have also demonstrated that Ssb can stimulate the dRpase activity of exonuclease I using double-stranded bacteriophage M13 DNA containing several strand interruptions at incised AP sites. These results suggest that Ssb may be required for efficient base-excision repair in bacteria.
 ...
PMID:Protein-protein interactions between the Escherichia coli single-stranded DNA-binding protein and exonuclease I. 861 28

HEX1/hExo1 is a Class III nuclease of the RAD2 family with 5' to 3' exonuclease and flap structure-specific endonuclease activities. HEX1/hExo1 is expressed at low levels in a wide variety of tissues, but at higher levels in fetal liver and adult bone marrow, suggesting HEX1/hExo1 is important for hematopoietic stem cell development. A putative HEX1/hExo1 promoter fragment extending from -6240 to +1600bp exhibits cell-type specific activity in transient transfection assays. This fragment directs high luciferase reporter gene expression in the hematopoietic cell line K562, chronic myelogenous leukemia cells, but low luciferase expression in the non-hematopoietic cell line HeLa, human cervical carcinoma cells. Deletion studies identified a fragment spanning -688 to +1600bp that exhibits full transcriptional activity while a slightly shorter fragment from -658 to +1600bp exhibits significantly decreased promoter activity. In vitro binding assays revealed DNA-binding activities that interact with -687 to -681bp and -665 to -658bp elements. Oligonucleotide competition and antibody disruption studies determined that the transcription factor CREB-1 recognizes the -687 to -681bp element, while transcription factors Sp1 and Sp3 recognize the -665 to -658bp element. Mutation of either the CREB-1 or Sp1/Sp3 binding sites dramatically reduces HEX1/hExo1 promoter activity and elimination of both elements abolishes promoter activity.
 ...
PMID:Identification of the human HEX1/hExo1 gene promoter and characterization of elements responsible for promoter activity. 1253 89

The mismatch repair process corrects errors in newly synthesized DNA. In this issue, Modrich and colleagues (Kadyrov et al., 2006) show that a component of the human mismatch repair machinery, MutLalpha, has endonuclease activity. MutLalpha introduces single-strand breaks near the mismatch and thus generates new entry points for the exonuclease EXOI to degrade the strand containing the mismatch.
 ...
PMID:MutLalpha: at the cutting edge of mismatch repair. 1687 62

Half of hereditary nonpolyposis colon cancer kindreds harbor mutations that inactivate MutLalpha (MLH1*PMS2 heterodimer). MutLalpha is required for mismatch repair, but its function in this process is unclear. We show that human MutLalpha is a latent endonuclease that is activated in a mismatch-, MutSalpha-, RFC-, PCNA-, and ATP-dependent manner. Incision of a nicked mismatch-containing DNA heteroduplex by this four-protein system is strongly biased to the nicked strand. A mismatch-containing DNA segment spanned by two strand breaks is removed by the 5'-to-3' activity of MutSalpha-activated exonuclease I. The probable endonuclease active site has been localized to a PMS2 DQHA(X)(2)E(X)(4)E motif. This motif is conserved in eukaryotic PMS2 homologs and in MutL proteins from a number of bacterial species but is lacking in MutL proteins from bacteria that rely on d(GATC) methylation for strand discrimination in mismatch repair. Therefore, the mode of excision initiation may differ in these organisms.
 ...
PMID:Endonucleolytic function of MutLalpha in human mismatch repair. 1687 53

We have developed a novel concept for enzymatic control of plasmonic coupling as a surface enhanced Raman scattering (SERS) nanosensor for DNA demethylation. This nanosensor is constructed by decorating gold nanoparticles (AuNPs) with Raman reporters and hemimethylated DNA probes. Demethylation of DNA probes initiates a degradation reaction of the probes by methylation-sensitive endonuclease Bsh 1236I and single-strand selective exonuclease I. This destabilizes AuNPs and mediates the aggregation of AuNPs, generating a strong plasmonic coupling SERS signal in response to DNA demethylation. This nanosensor has the advantages in its high signal-to-noise ratio, superb specificity, and rapid, convenient, and reproducible detection with homogeneous, single-step operation. Thus, it provides a useful platform for detecting DNA demethylation and related molecular diagnostics and drug screening. This work is the first time that enzymatic degradation of DNA substrate probes has been utilized to induce aggregation of AuNPs such that reproducible, sensitive SERS signals can be achieved from biological recognition events. This enzymatic control mechanism for plasmonic coupling may create a new paradigm for the development of SERS nanosensors.
 ...
PMID:Enzymatic control of plasmonic coupling and surface enhanced Raman scattering transduction for sensitive detection of DNA demethylation. 2299 23

We synthesized long, nucleobase-modified, single-stranded DNA (ssDNA) using terminal deoxynucleotidyl transferase (TdT) enzymatic polymerization. Specifically, we investigated the effect of unnatural nucleobase size and incorporation density on ssDNA resistance to exo- and endonuclease degradation. We discovered that increasing the size and density of unnatural nucleobases enhances ssDNA resistance to degradation in the presence of exonuclease I, DNase I, and human serum. We also studied the mechanism of this resistance enhancement using molecular dynamics simulations. Our results show that the presence of unnatural nucleobases in ssDNA decreases local chain flexibility and hampers nuclease access to the ssDNA backbone, which hinders nuclease binding to ssDNA and slows its degradation. Our discoveries suggest that incorporating nucleobase-modified nucleotides into ssDNA, using enzymatic polymerization, is an easy and efficient strategy to prolong and tune the half-life of DNA-based materials in nucleases-containing environments.
 ...
PMID:Enzymatic Synthesis of Nucleobase-Modified Single-Stranded DNA Offers Tunable Resistance to Nuclease Degradation. 3001 Nov 92


<< Previous 1 2