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)

A DNA fragment (1.4 Kb) which codes for 5' region of 35S ribosomal precursor RNA (pre-rRNA) in Tetrahymena pyriformis was cloned with pBR322. The fragment was cleaved from the central part of the palindromic rDNA with restriction endonuclease KpnI and HindIII, and ligated to the larger moiety of pBR322 DNA-HindIII-BamHI fragment together with lambda DNA-KpnI-BamHI fragment through trimolecular ligation. The analysis of R-loop formed between KpnI-linearized recombinant plasmid and 35S pre-rRNA revealed a DNA:RNA hybrid region of 465 +/- 30 base pairs in length. Considering the contraction of DNA:RNA hybrids relative to DNA duplexes (Philippsen et al., J. Mol. Biol., 123, 387-404, 1978), the size of the hybrid region was corrected to about 490 base pairs. Alternatively, the size of DNA which was protected against nuclease S1 due to hybrid formation with 35S pre-rRNA was estimated to be 490 nucleotides long. These data indicate that the transcription initiation site is localized at about 490 base pairs from the HindIII site of the cloned rDNA fragment.
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PMID:Localization of putative transcription initiation site on the cloned rDNA fragment of Tetrahymena pyriformis. 627 12

To study the molecular basis for lack of expression of the simian virus 40 (SV40) early region genes in murine teratocarcinoma-derived stem cells, we introduced a recombinant plasmid consisting of pBR322 linked to the herpes simplex virus type 1 thymidine kinase gene and SV40 genome into thymidine kinase-deficient F9 stem cells. The resulting stem cell clone, 12-1, and a retinoic acid-induced differentiated daughter cell clone, 12-1a, each contain one copy per cell of the entire recombinant plasmid integrated into the cellular genome through a site on the pBR322 genome. Restriction endonuclease analyses indicate that there is no difference in integration site or organization of the three component parts of the plasmid genome within cellular DNA of stem and differentiated cells; yet the differentiated cells, 12-1a, express SV40 large tumor antigen whereas the stem cells, 12-1, do not. Both stem and differentiated cells produce two size classes of polyadenylylated RNA, 2900 and 2600 bases in length, homologous to the early region of the SV40 genome, detectable by RNA blotting analysis. S1 nuclease analysis of the SV40 transcripts present in stem and differentiated cells indicate that the SV40 mRNAs were identically spliced in the two cell types, in a manner consistent with that observed for spliced large and small tumor antigen mRNAs in SV40-infected monkey kidney cells. Thus, the failure of 12-1 teratocarcinoma stem cells, containing an integrated SV40 genome, to express SV40 tumor antigen is not due to a lack of transcription of the SV40 early region or to an inability to splice primary transcripts.
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PMID:Transcription of the simian virus 40 genome in DNA-transformed murine teratocarcinoma stem cells. 627 68

Three assays have been designed to detect the cleavage of duplex phi X174 DNA at single-base mis-matches. Studies with S1 nuclease failed to detect cleavage at mis-matches. S1 nuclease digestion at 37 and 55 degrees C failed to produce a preferential degradation of a multiply mis-matched heteroduplex when compared to a mis-match-free homo-duplex as analyzed by sedimentation on sucrose gradients. Other heteroduplex templates were not cleaved by S1 nuclease at a defined single-base mis-match when assayed by gel electrophoresis or by marker rescue. In all cases, the amount of S1 nuclease employed was at least 10-times more than that required to render a single-stranded phi X174 DNA molecule completely acid soluble. The rate of hydrolysis of single-base mis-matches by S1 nuclease was estimated to be less than 0.016% of the rate at a base in single-strand phi X174 DNA. In no instance did we detect activity by S1 nuclease directed at mis-matched sites in our template molecules. Similarly, the single-strand specific endonuclease from Neurospora crassa does not cleave heteroduplex templates at a defined single-base mis-match when assayed by marker rescue.
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PMID:S1 nuclease does not cleave DNA at single-base mis-matches. 627 10

The state of rabbit (Shope) papilloma virus DNA in virus-induced nonproducing tumors on domestic rabbits was investigated. Virus-specific sequences were resolved into many distinct bands by one-dimensional agarose gel electrophoresis. Two-dimensional gel electrophoresis, CsCl/propidium iodide density equilibrium centrifugation, partial digestion with a restriction endonuclease, and S1 nuclease digestion permitted us to identify the bands as free viral episomes representing circular molecules of increasing size. In some tumors (both papillomas and carcinomas), up to 25% of the virus-specific DNA was linear and comigrated with cellular DNA. Integration of at least some of these sequences was suggested by the detection of viral-cellular junction bands in one tumor after digestion of DNA with EcoRI and Sal I, enzymes that cut Shope DNA once. Finally, the physical states of viral DNA in papillomas and carcinomas were found to be similar, although free episomes were generally larger in carcinomas.
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PMID:Variable-sized free episomes of Shope papilloma virus DNA are present in all non-virus-producing neoplasms and integrated episomes are detected in some. 627 94

We studied the synthesis of B-tropic murine leukemia viral DNA in vitro by detergent-disrupted virions. The reaction products (detected by the Southern transfer technique) included full-length, infectious, double-stranded DNA and several subgenomic fragments. Restriction endonuclease analysis and hybridization and specific probes revealed two classes of subgenomic fragments: some were derived from the right end of the genome, and some were derived from the left end. Most of the fragments harbored one long terminal repeat copy at their ends, suggesting that they were initiated correctly. S1 nuclease and restriction endonuclease treatments of these fragments indicated that a single-stranded gap was present near the first initiation site of plus strong-stop DNA. The treatments also suggested the presence of a second initiation site flanked by a single-stranded gap 0.9 kilobase pairs from the right end of the genome. Our data clearly show that plus-strand DNA is synthesized at both ends of the genome, by using plus strong stop as the first initiation site and additional initiation sites.
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PMID:Synthesis of murine leukemia viral DNA in vitro: evidence for plus-strand DNA synthesis at both ends of the genome. 628 52

Purified DNA was modified in vitro by 3H-labelled O-acetyl or O,O'-diacetyl-4-hydroxyaminoquinoline-1-oxide (Ac4HAQO or di Ac-4HAQO). It was then subjected to the action of the single-stranded DNA specific nuclease S1 and the digested fractions were analysed. For both types of modified DNA, the release of non-modified nucleotides was faster than the release of modified nucleotides. This result is at variance with that obtained with acetoxy-acetylaminofluorene-modified DNA: in the latter case, the modified nucleotides were preferentially released. The results suggest that the S1 endonuclease can recognize different conformational changes in DNA, which depend on the carcinogen used. The enzymatic activity (or activities) present in Micrococcus luteus cell extracts released ethanol-soluble products from Ac-4HAQO modified DNA.
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PMID:In vitro enzymatic recognition of DNA modified by O,O'-diacetyl or O-acetyl derivatives of the carcinogen 4-hydroxyaminoquinoline-1-oxide. 628

The magnitude of the genetic relatedness of the two antigenic subtypes of equine herpesvirus 1 (EHV-1) was determined by DNA-DNA reassociation kinetics. Denatured, labeled viral DNA from one EHV-1 subtype was allowed to reassociate in the presence or absence of the unlabeled heterologous viral DNA. The initial rate of reassociation of either labeled viral DNA was increased by the presence of the heterologous viral DNA to an extent indicating 10 to 20% homology between the two EHV-1 genomes. Similar estimates of the amount of homology between the genomes of the two EHV-1 subtypes were obtained by determining the maximum fraction of labeled viral DNA that could be made resistant to S1 nuclease by hybridization with a large molar excess of the unlabeled, heterologous viral DNA. Analysis of the thermal stability of the subtype 1-subtype 2 heteroduplex DNA indicated approximately 30% base pair mismatching within the hybrid DNA molecules. Cross-hybridization of 32P-labeled virion DNA to nitrocellulose blots of restriction endonuclease cleavage fragments of each EHV-1 subtype DNA indicated that the observed homology between the two viruses was nonuniformly distributed with the viral genome. No homology could be detected between the DNA of either EHV-1 subtype and that of a strain of equine cytomegalovirus (EHV-2). The data suggest that the two biotypes of EHV-1 have arisen by divergent evolution from a common progenitor herpesvirus.
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PMID:Assessment of the base sequence homology between the two subtypes of equine herpesvirus 1. 629 88

The alkaline zinc-metallo nuclease of Physarum polycephalum is an endonuclease with a high specificity for single-stranded nucleic acids. Single-stranded DNA was cleaved at least 6,000 times faster than double-stranded DNA under identical conditions. In the supercoil-induced single-stranded region of Form I PM2 DNA only a single nick was made. The nuclease showed nucleotide specificity. Poly(A), poly(I), and poly(dT) were preferentially hydrolyzed. Product analysis showed that it acted by an endonucleolytic mechanism: long polynucleotides were fragmented via intermediate length products to oligo- and mono-nucleotides with the phosphate group at the 5'-terminal position. Extensive similarities exist with the single-strand-specific nuclease S1 from Aspergillus. The zinc-metallo endonuclease from Physarum could be used as a similar probe for single-stranded nucleic acids at neutral or alkaline pH conditions.
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PMID:Substrate specificity and mode of action of the zinc-metallo nuclease from Physarum polycephalum. 629 65

A rat liver DNA genomic library was prepared using the lambda phage cloning vector Charon 28. Recombinant phage were screened with a cDNA clone (pOR-7) containing sequences complementary to mRNA coding for NADPH-cytochrome P-450 oxidoreductase. This cDNA clone contains the poly(A) addition site and 60% of the mRNA sequence (Gonzalez, F. J., and Kasper, C. B. (1982) J. Biol. Chem. 257, 5962-5968). Four positive phage were identifed and plaque-purified, and their DNA was isolated and subjected to restriction endonuclease mapping. All phage DNA inserts, which ranged from 11 to 16 kilobases, contained several overlapping restriction fragments. The clone with the largest insert (lambda OR-2) was found to contain restriction fragments identical with those of rat DNA when both were subjected to Southern blotting with nick-translated pOR-7 DNA; this finding established the presence in lambda OR-2 of the 3' end (poly(A) addition site) of the oxidoreductase gene. When [32P]cDNA synthesized from enriched oxidoreductase poly(A) RNA was utilized as a probe, additional fragments were identified. The fragment most distal to the 3'-specific fragment was assumed to contain the 5' cap site and was subcloned into pBR322 for further analysis. Restriction mapping and Southern blot analysis further localized the 5' end of the gene to an AvaII fragment of 540 base pairs (bp). Hybridization of this fragment with oxidoreductase mRNA-enriched poly(A) RNA resulted in the arrest of translation of oxidoreductase; this confirmed that it contained an exon region of the oxidoreductase gene. S1 nuclease mapping and DNA sequencing identified to within +/- 1 bp the 5' cap site of the gene which corresponds to an A start. DNA sequencing of the 5'p flanking region revealed no "TATA box" in the vicinity of -25 to -30 bp of the cap site. R-loop analysis of lambda OR-2 revealed the presence of a minimum of seven introns in the 6000-bp oxidoreductase gene and eight exons with a total length of approximately 2600 bp.
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PMID:Cloning and characterization of the rat NADPH-cytochrome P-450 oxidoreductase gene. 629 77

Selective transcription of hybrid plasmids containing yeast rDNA was achieved with a template-dependent S100 fraction from whole cell extracts of Saccharomyces cerevisiae. A small region of the yeast rDNA which directs selective initiation in vitro was identified by subcloning. An initiation site was mapped within this region on the basis of the molecular weights of transcripts synthesized in vitro from templates which were cleaved with restriction endonucleases at a series of sites downstream from the site of initiation. The initiation site maps to a position 3.0 kilobase pairs upstream from the sequences which encode the 5' terminus of 18 S rRNA. In vitro initiation from this site is not inhibited by 50 micrograms/ml of alpha-amanitin and is completely abolished when the reactions contain 0.2 M (NH4)2SO4. Based on these data, selective transcription of yeast rDNA in vitro is RNA polymerase I-dependent. Several S1 nuclease-resistant hybrids are formed between DNA probes labeled at restriction endonuclease sites downstream from the in vitro initiation site and high molecular weight cellular RNA. The 5' terminus of the most abundant rRNA precursor maps approximately 0.7 kilobase pair upstream from sequences which encode the 5' terminus of 18 S rRNA. This corresponds to the 5' terminus of the 35 S rRNA precursor reported by others. The 5' terminus of the largest detectable precursor synthesized in vivo corresponds closely with the initiation site identified in vitro. Based on the data presented here, RNA polymerase I traverses the interspersed 5 S rRNA gene. Since these two ribosomal genes are transcribed in opposite directions, this arrangement of the RNA polymerase I and III promoters may ensure that equivalent amounts of the two gene products are synthesized in vivo.
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PMID:RNA polymerase I-dependent selective transcription of yeast ribosomal DNA. Identification of a new cellular ribosomal RNA precursor. 629 29


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