Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.30.2 (endonuclease)
18,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The cistron A protein induced by phage varphiX174 nicks (produces a single-strand break in) the viral strand of the superhelical varphiX duplex DNA, thereby forming a complex with the DNA. The protein, seen bound to the DNA in the electron microscope, was located in the restriction endonuclease fragment between nucleotides 4290 and 4330 on the varphiX map [Sanger, F., Air, G. M., Barrel, B. G., Brown, N. L., Coulson, A. R., Fiddes, J. C., Hutchison, C. A., III, Slocomb, P. M. Y. & Smith, M. (1977) Nature 265, 687-695]. Replication also was initiated at this point, thus identifying the site of cistron A protein nicking and binding as the origin of replication. The cisA-DNA complex (separated from free cistron A protein), upon the addition of Escherichia coli rep protein, ATP, and DNA binding protein, is unwound to generate a single-stranded linear [presumably the nicked (+) strand] and a circular [presumably the (-) strand] molecule. The cisA-DNA complex, upon the further addition of DNA polymerase III holoenzyme and deoxynucleoside triphosphates, supports replication to generate viral, single-stranded circles, as many as 15 circles per cisA-DNA complex. The replicating intermediates seen in the electron microscope are a novel form of "rolling circle" [Gilbert, W. & Dressler, D. H. (1969) Cold Spring Harbor Symp. Quant. Biol. 33, 473-485]. The 5' end (presumably with the cistron A protein bound to it) is locked in the replication fork and loops back to accompany the strand-separation and replication fork around the template [(-) strand] circle. Thus, the multiple functions of cistron A protein include: (i) nicking the viral strand at the origin of replication to initiate a round of replication, (ii) participating in a complex which supports fork movement in strand separation and replication, (iii) nicking again at the regenerated origin to produce a unit-length DNA, and (iv) ligating the newly generated 3'-OH end to the 5'-phosphate-complexed end to form a circular viral molecule.
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PMID:phiX174 cistron A protein is a multifunctional enzyme in DNA replication. 26 83

The nucleotide sequence of the entire 5' untranslated region of human gamma-globin mRNA has been determined. This was accomplished by analyzing complementary DNA (cRNA) synthesized from the mRNA with reverse transcriptase. The CDNA was labeled at its 3' end with 32"p using terminal deoxynucleotidyl transferase, digested with the restriction endonuclease Hae III and the end-labeled fragment isolated ans sequenced by the method of Maxam and Gilbert. Including the initiation codon AUG, the 5' untranslated region of human gamma-globin mRNA contains 57 nucleotides, compared to 41 in alpha- and 54 in beta-globin mRNA. There is very little homology between alpha and gamma sequences in the 5' region. There is considerable homology between beta- and gamma-globin mRNAs in the regions proximal and distal to the initiation codon, but the entire sequence shows less homology than the human and rabbit beta-globin mRNAs. The hexanucleotide sequence CUUCUG is found near the 5' ends of all three human globin mRNAs, suggesting a possible role of this sequence or ribosomal binding. Both guanosine and cytidine were found at the 19th nucleotide position from the 5' end of the gamma mRNA. We believe this heterogeneity arises from the difference in nucleotide sequence between the A gamma and G gamma loci.
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PMID:The nucleotide sequence of the 5' untranslated region of human gamma-globin mRNA. 31 62

A guanine-rich single-stranded DNA from the human immunoglobulin switch region was shown by Sen and Gilbert [Nature, (1988) 334, 364-366] to be able to self-associate to form a stable four-stranded parallel DNA structure. Topoisomerase II did not cleave the single-stranded DNA molecule. Surprisingly, the enzyme did cleave the same DNA sequence when it was annealed into the four-stranded structure. The two cleavage sites observed were the same as those found when this DNA molecule was paired with a complementary molecule to create a normal B-DNA duplex. These cleavages were shown to be protein-linked and reversible by the addition of salt, suggesting a normal topoisomerase II reaction mechanism. In addition, an eight-stranded DNA molecule created by the association of a complementary oligonucleotide with the four-stranded structure was also cleaved by topoisomerase II despite being resistant to restriction endonuclease digestion. These results suggest that a single strand of DNA may possess the sequence information to direct topoisomerase II to a binding site, but the site must be base paired in a proper manner to do so. This demonstration of the ability of a four-stranded DNA molecule to be a substrate for an enzyme further suggests that these DNA structures may be present in cells.
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PMID:Eukaryotic topoisomerase II cleavage of parallel stranded DNA tetraplexes. 131 62

A DNA fragment of about 3.4 kilobase pairs that expressed the HgaI modification activity was cloned from the chromosomal DNA of Haemophilus gallinarum, and its nucleotide sequence was determined. Two open reading frames (ORF) which could code for structurally similar proteins were identified in the upstream and middle regions and a truncated ORF in the downstream region in the same orientation. When the respective ORFs were separately cloned, the clones carrying the upstream and middle ORFs both expressed the modification activity, indicating that the two genes are involved in modification of the HgaI restriction-modification system. In order to determine the sites of modification precisely, the respective genes were recloned into an expression vector, from which gene products were purified. A short DNA fragment carrying the HgaI recognition site was treated with each of these enzymes, and, after separation of the two strands by duplex formation with M13 viral DNAs carrying the respective strands, the presence or absence of modification was judged from susceptibility to HgaI endonuclease. The results of analysis showed that different strands were modified in an asymmetric way by each gene product. Analysis of the species and positions of modified bases by the Maxam-Gilbert method further demonstrated that the gene products from the upstream and middle ORFs participated in methylation of the internal cytosine residues of the strands carrying 3'-CTGCG-5' and 5'-GACGC-3', respectively. We concluded that the HgaI modification system consisted of two cytosine methylase genes responsible for modification of different strands in the target DNA.
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PMID:The HgaI restriction-modification system contains two cytosine methylase genes responsible for modification of different DNA strands. 185 24

We have developed a strategy by which the nature of phosphodiester bond breaks produced by various DNA-repair endonucleases and also other nucleases, can be characterized. A purified apurinic/apyrimidinic (AP) specific endonuclease from a permanently established mouse plasmacytoma cell-line (MPC-11) has been examined with respect to the exact incision site generated at the baseless site. By the aid of enzymatic treatment with calf intestinal phosphatase, the 3'-phosphatase activity of T4-polynucleotide kinase, chemical modification with piperidine in addition to the Maxam-Gilbert sequencing procedure, followed by separation on a DNA-sequencing gel, the nature of the cleaved phosphodiester bond, both 3' and 5' to the cleavage site, has been established. The AP-specific endonuclease investigated was classified as a class II AP-endonuclease according to the four possible classes of AP-endonuclease with respect to the termini produced. By use of this technique each single damaged and cleaved site can be investigated separately.
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PMID:Analysis of cleavage products of DNA repair enzymes and other nucleases. Characterization of an apurinic/apyrimidinic specific endonuclease from mouse plasmacytoma cells. 245 3

An apurinic/apyrimidinic (AP) specific endonuclease from mouse plasmacytoma cells (line MPC-11), was observed to cleave apurinic sites in oligonucleotides 9, 11, 12, 39 and 40 nucleotides in length. However, the enzyme failed to cleave AP-sites in two oligonucleotides 7 nucleotides in length. The maximum rates of digestion observed on these short single-stranded DNA (ssDNA) fragments were approximately 1/30 of the rates observed on double-stranded DNA (dsDNA). In studies using the Maxam-Gilbert DNA sequencing analysis, apurinic sites in purine-rich regions were preferentially cleaved in dsDNA but not in ssDNA, indicating that the enzyme has a sequence preference on dsDNA. These results suggest that some sites on DNA might be more efficiently repaired than others.
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PMID:Action of a mammalian AP-endonuclease on DNAs of defined sequences. 246 39

The characterization of MvaI restriction-modification enzymes, isolated from Micrococcus varians RFL19, is reported. Both enzymes recognize the 5'CC decreases (A/T)GG nucleotide sequence. The endonuclease cleaves the sequence at the position indicated by the arrow, whereas the methylase modifies the internal cytosine, yielding N4-methylcytosine. This type of modification protects the substrate from R.MvaI cleavage. 5-Methylcytosine in the same position of the recognition sequence does not protect the substrate from R.MvaI cleavage. R.MvaI proved to be the first example of a restriction endonuclease differentiating the position of the methyl group in the heterocyclic ring of cytosine, located in the same site of the recognition sequence. M.MvaI modifies DNA dcm+ in vitro yielding N4,5-dimethylcytosine. N4-methylcytosine cannot be differentiated from cytosine using the Maxam-Gilbert DNA sequencing procedure.
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PMID:Investigation of restriction-modification enzymes from M. varians RFL19 with a new type of specificity toward modification of substrate. 299 11

The Bacillus subtilis gene (pyrB), which encodes aspartate transcarbamylase (ATCase), was cloned on a HindIII restriction endonuclease fragment inserted into the pUC13 plasmid vector. B. subtilis pyrB was expressed in Escherichia coli, as judged by complementation of E. coli pyrB mutants and production of enzyme that was specifically inhibited by antibody directed against B. subtilis ATCase. The extent of expression was strongly dependent on the orientation of the inserted DNA in the vector, which suggested that transcription was initiated from vector-borne (rather than B. subtilis) promoters. The entire 1098-base pair HindIII fragment of B. subtilis DNA was sequenced by the Maxam-Gilbert method. The amino acid sequence of B. subtilis ATCase was deduced from a 305-codon open reading frame and agreed very well with analyses of the purified enzyme. Comparison of the sequence of B. subtilis ATCase with that of E. coli ATCase catalytic subunit, for which the three-dimensional structure is known, revealed many homologous residues of probable importance in catalysis and structural folding of ATCases. The significance of homology to E. coli ornithine transcarbamylases was also analyzed. The sequences of the 5' and 3' flanking regions to pyrB encode open reading frames in both cases which overlap with pyrB by eight and six codons, respectively. It is probable that these open reading frames encode other enzymes of a coordinately regulated unit. The sequence 5' to pyrB also encodes an mRNA bearing a pyrimidine-rich sequence followed by a typical sequence for a rho-independent transcription terminator. The presence of these elements and the 5' open reading frame suggest that B. subtilis pyrB, like E. coli pyrBI, is regulated by an attenuation mechanism.
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PMID:Cloning and structure of the Bacillus subtilis aspartate transcarbamylase gene (pyrB). 301 59

Restriction fragments of HBV-DNA, cleaved by endonuclease HhaI, containing HBcAg gene were trimmed by BAL-31 exonuclease to remove different lengths of the precore sequence. They were inserted into plasmid pUR222 at EcoRI site through synthetic linker ligation. Transformants in E. coli BMH7118 showing different levels of HBcAg gene expression were screened and analyzed for their nucleotide sequences in the junction region both by Maxam and Gilbert's chemical degradation method and by M13 chain termination method. Results of sequence analysis of different transformants revealed a partial palindromic (loop and stem) structure, at -7 to -35 nucleotide with regard to ATG of the HBcAg gene as position +1, which has dramatic effect on the level of expression of the inserted gene using the same promoter, SD sequence and identical N-terminus. The amount of HBcAg synthesized differed from 9% in the high expressing plasmid to less than 0.01% of the total cell proteins in the low expressing transformants. The findings were compared to results obtained by other workers in studies of HBcAg expression in procaryotes and their significance in the expression of eucaryotic genes in procaryotic cells were discussed.
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PMID:Structure in the precore region of hepatitis B core gene affecting its expression in E. coli. 333 Aug 77

DNA damages caused by various anticancer nitrosourea compounds such as ACNU and MCNU were studied. Reiterated fragments of 167 and 203 base pairs (bp) were obtained after Hind III and Hae III restriction endonuclease digestion of 9L rat brain tumor DNA. The end-labeled reiterated fragments were reacted with ACNU and MCNU, which resulted in the scission breaks corresponding to the locations of guanine on an extended Maxam-Gilbert sequencing gel. Subsequent piperidine hydrolysis yielded scission products more frequently. These results indicate that nitrosoureas such as ACNU and MCNU generate DNA scission breaks and/or alkali-labile sites preferentially at the position of guanine moieties in rat brain tumor DNA.
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PMID:[Analysis of DNA damage induced by nitrosourea derivatives in rat brain tumor cells using a sequencing procedure]. 342 52


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