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)

An acid deoxyribonuclease has been purified from rat small intestinal mucosa by a procedure including ammonium sulfate fractionation, chromatographies on DEAE-cellulose, CM-cellulose and SE-Sephadex and finally isoelectric focusing. Polyacrylamide gel electrophoresis of the purified enzyme preparation showed one major and two minor bands, and the enzyme activity corresponded to one of the minor bands. The enzyme preparation was free of contaminating DNase I, DNase III, alkaline RNase, acid and alkaline phosphatases and nonspecific phosphodiesterase, but slight activities of DNase IV and acid RNase were detected. The enzyme did not require divalent cations for activity, had a pH optimum of 4.5 in 0.33 M sodium acetate buffer, and had an optimum temperature of 50 to 60 degrees C when assayed for 30 min. The rate of hydrolysis of native DNA was about 2.5-fold faster than that observed with denatured DNA. Its molecular weight was found to be 9.0 +/- 0.1. The enzyme catalyzes the endonucleolytic cleavage of native and denatured DNA, yielding oligonucleotides which have an average chain length of about 7, and which contain 3'-phosphoryl termini. The mode of action of the enzyme is double-strand scission.
 ...
PMID:Purification and properties of an acid deoxyribonuclease from rat small intestinal mucosa. 663 Jan 62

In eukaryotic cells, a 5'-flap DNA endonuclease and a double-stranded DNA 5'-exonuclease activity reside within a 42-kDa enzyme called FEN-1 (flap endonuclease-1 and 5(five)'-exonuclease). This endo/exonuclease has been shown to be highly homologous to human XP-G, Saccharomyces cerevisiae RAD2, and S. cerevisiae YKL510. Like FEN-1, these related structure-specific nucleases recognize and cleave a branched DNA structure called a DNA flap and its derivative, called a pseudo Y-structure. To dissect the important structural components of the DNA flap structure, we have developed a mobility shift assay. We find that the Fadj strand (located adjacent to the displaced flap strand) is necessary for efficient binding and cleavage of flap structures by FEN-1. When this strand is absent or when it is present, but recessed from the elbow of the flap strand, binding efficiency drops. Further investigation of the role of the Fadj strand using double flap structures reveals that the Fadj strand is necessary to provide a double-stranded template upon which FEN-1 can bind near the elbow of the flap strand. These results provide a basis for understanding how this structure-specific nuclease recognizes a variety of DNA substrates.
 ...
PMID:DNA structural elements required for FEN-1 binding. 787 18

In eukaryotic cells, a 5' flap DNA endonuclease activity and a ds DNA 5'-exonuclease activity exist within a single enzyme called FEN-1 [flap endo-nuclease and 5(five)'-exo-nuclease]. This 42 kDa endo-/exonuclease, FEN-1, is highly homologous to human XP-G, Saccharomyces cerevisiae RAD2 and S.cerevisiae RTH1. These structure-specific nucleases recognize and cleave a branched DNA structure called a DNA flap, and its derivative called a pseudo Y-structure. FEN-1 is essential for lagging strand DNA synthesis in Okazaki fragment joining. FEN-1 also appears to be important in mismatch repair. Here we find that human PCNA, the processivity factor for eukaryotic polymerases, physically associates with human FEN-1 and stimulates its endonucleolytic activity at branched DNA structures and its exonucleolytic activity at nick and gap structures. Structural requirements for FEN-1 and PCNA loading provide an interesting picture of this stimulation. PCNA loads on to substrates at double-stranded DNA ends. In contrast, FEN-1 requires a free single-stranded 5' terminus and appears to load by tracking along the single-stranded DNA branch. These physical constraints define the range of DNA replication, recombination and repair processes in which this family of structure-specific nucleases participate. A model explaining the exonucleolytic activity of FEN-1 in terms of its endonucleolytic activity is proposed based on these observations.
 ...
PMID:Processing of branched DNA intermediates by a complex of human FEN-1 and PCNA. 866 33

Eukaryotic flap-endonuclease (FEN-1) is 42-kD single-subunit structure-specific nuclease that cleaves 5'-flap strands of the branched DNA structure and possesses 5'-exonuclease activity. FEN-1 participates in DNA replication, repair, and recombination. The interaction of FEN-1 with DNA structures generated during replication and repair was studied using two types of photoreactive oligonucleotides. Oligonucleotides bearing a photoreactive arylazido group at the 3'-end of the primer were synthesized in situ by the action of DNA polymerase beta using base-substituted photoreactive dUTP analogs as the substrates. The photoreactive group was also bound to the 5'-end phosphate group of the oligonucleotide by chemical synthesis. Interaction of FEN-1 with both 5'- and 3'-ends of the nick or with primer-template systems containing 5'- or 3'-protruding DNA strands was shown. Formation of a structure with the 5'-flap containing the photoreactive group results in decrease of the level of protein labeling caused by cleavage of the photoreactive group due to FEN-1 endonuclease activity. Photoaffinity labeling of proteins of mouse fibroblast cell extract was performed using the radioactively labeled DNA duplex with the photoreactive group at the 3'-end and the apurine/apyrimidine site at the 5'-end of the nick. This structure is a photoreactive analog of an intermediate formed during DNA repair and was generated by the action of cell enzymes from the initial DNA duplex containing the 3-hydroxy-2-hydroxymethyltetrahydrofurane residue. FEN-1 is shown to be one of the photolabeled proteins; this indicates possible participation of this enzyme in base excision repair.
 ...
PMID:Affinity labeling of flap-endonuclease FEN-1 by photoreactive DNAs. 1156 52