Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.21.1 (DNase)
 7,655 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

DNA polymerase I (pol I) from Escherichia coli has three well-defined activities: DNA polymerase, 3'-5' exonuclease, and 5'-3' exonuclease. We have raised monoclonal antibodies to pol I which selectively neutralize each of these three activities, thus supporting the model of separate active sites for each activity, heretofore exclusively demonstrated with proteolytic fragments of pol I. Antibodies from each class could bind pol I in the presence of antibodies of another class, indicating the existence of significant spatial separation between each of the three sites. In addition, several of the neutralizing antibodies were able to distinguish particular activities of the 5'-3' exonuclease. One of them, for example, inhibited the RNase H activity but not the DNase activity. Two other antibodies could, in addition to inhibiting the polymerase and the 3'-5' exonuclease, either stimulate or inhibit the 5'-3' exonuclease depending upon the assay conditions, particularly the ionic strength.
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PMID:Selective immunoneutralization of the multiple activities of Escherichia coli DNA polymerase I supports the model for separate active sites and indicates a complex 5' to 3' exonuclease. 132 12

Previous studies from this laboratory have characterized a 174 bp enhancer element which is located 2 kb upstream of the initiation site. Half of the enhancer action is controlled by a 37 bp element at the 3' end of the 174 bp region. We now report that a 43 bp adjacent domain which is located upstream of the 37 bp element constitutes an additional motif of the rDNA enhancer. When the plasmid consisting of the 43 bp DNA upstream of the rDNA core promoter was transcribed in a fractionated rat tumor cell extract (fraction DE-B), transcription of rDNA was augmented 4 fold. Electrphoretic mobility shift and DNAase I footprinting analyses showed that the purified 37 bp enhancer (E1)-binding protein, (E1BF) not only interacted with the enhancer motif E1 but also interacted with the neighbouring 43 bp enhancer domain E2. The specificity of the binding was demonstrated by competition with unlabelled 37 bp and 43 bp fragment and lack of competition with nonspecific DNAs in the mobility shift assay. These studies have shown that a single pol I transcription factor can bind to multiple enhancer domains with no significant sequence homologies and such multiple interactions may result in maximal transcription of ribosomal gene from the core promoter.
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PMID:Multiple functional enhancer motifs of rat ribosomal gene. 192 95

We have made a computer-assisted search for homology among polymerases or putative polymerases of various viruses and a transposable element, the Drosophila copia-like element 17.6. The search revealed that the putative polymerase (second open reading frame) of the copia-like element 17.6 bears close resemblance in overall structural organization to the pol gene product of Moloney murine leukaemia virus (M-MuLV): they show significant homology to each other at both the N- and C-terminal portions, suggesting that the 17.6 putative polymerase carries two enzymatic activities, related to reverse transcriptase and DNA endonuclease. The putative polymerase of cauliflower mosaic virus (CaMV) shows striking homology with the putative polymerase of 17.6 over almost its entire length, but it lacks the DNA endonuclease-related sequence. Furthermore, it was shown that the N-terminal ends of the M-MuLV pol product and the CaMV and 17.6 putative polymerases exhibit strong sequence homology with the gag-specific protease (p15) of Rous sarcoma virus (RSV) as well as the amino acid sequence predicted from the gag/pol spacer sequence of human adult T-cell leukaemia virus (HTLV). These p15-related sequences contain a highly conserved stretch of amino acids which show a close similarity with sequences around the active site amino acids Asp-Thr-Gly of the acid protease family, suggesting that they have an activity similar to acid protease. On the basis of the alignment of reverse transcriptase-related sequences, a dendrogram representing phylogenetic relationships among all the viruses compared together with 17.6 was constructed and its evolutionary implication is discussed.
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PMID:Close structural resemblance between putative polymerase of a Drosophila transposable genetic element 17.6 and pol gene product of Moloney murine leukaemia virus. 240 86

The avian retroviral pol gene-encoded DNA endonuclease (pol-endo) has been shown to selectively cleave the viral long terminal repeat sequences (LTRs) in single-stranded DNA substrates in a region known to be joined to host DNA during integration (G. Duyk, J. Leis, M. Longiaru, and A.M. Skalka, Proc. Natl. Acad. Sci. USA 80:6745-6749, 1983). The preferred sites of cleavage were mapped to the unique U5/U3 junctions found only in covalently closed circular DNA molecules containing two tandem LTRs. The cuts occurred three nucleotides 5' to the axis of symmetry of the 12-of-15-base-pair nearly perfect inverted repeat which marks the LTR junction. Experiments with double-stranded supercoiled DNA substrates revealed a similar specificity for nicking. Also, the endonuclease associated with the pol cleavage product, pp32, has the same specificity as the alpha beta form. The limits of sequence required for site-selective cleavage near the U5/U3 junction were established with single-stranded DNA substrates. A domain no larger than 44 base pairs allowed site-selective cleavage in each strand in vitro. Recognition of either strand appeared to be independent of the other, and in each case, the critical sequence was asymmetrically distributed with respect to the U5/U3 junction. The predominant contribution was from the U5 domain; this is consistent with its conservation in the LTR sequences of a number of avian sarcoma and leukosis viruses.
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PMID:Circles with two tandem long terminal repeats are specifically cleaved by pol gene-associated endonuclease from avian sarcoma and leukosis viruses: nucleotide sequences required for site-specific cleavage. 241 65

The gag-pol precursor protein of the avian sarcoma-leukosis virus is processed into three known pol-encoded mature polypeptides; the 95- and 63-kilodalton (kDa) beta and alpha subunits, respectively, of reverse transcriptase and the 32-kDa pp32 protein. The pp32 protein possesses DNA endonuclease activity and is produced from the precursor by two proteolytic cleavage events, one of which removes 4.1 kDa of protein from the C terminus. A 36-kDa protein (p36pol) which retains this C-terminal segment is detectable in small quantities in virions. We have constructed Escherichia coli plasmid clones that express the C-terminal domains of pol corresponding to pp32 and p36. These proteins have been purified by column chromatographic methods to near homogeneity. No significant differences could be detected in the enzymatic properties of the bacterially produced p32pol and p36pol proteins. Both possess DNA endonuclease activity and, like the pp32 protein isolated from virions, can cleave near the junction of two tandem avian sarcoma-leukosis virus long terminal repeats in double-stranded supercoiled DNA substrates. In the presence of Mg2+, both p32pol and viral pp32 cleave either strand of DNA 2 nucleotides 5' to the junction.
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PMID:Properties of avian sarcoma-leukosis virus pp32-related pol-endonucleases produced in Escherichia coli. 283 18

We determined the complete nucleotide sequence of the intracisternal A-particle gene, IAP-H18, cloned from the normal Syrian hamster liver DNA. IAP-H18 was 7,951 base pairs in length with two identical long terminal repeats of 376 base pairs at both ends. On the coding strand, imperfect open reading frames corresponding to gag and pol of the retrovirus genome were observed, whereas many stop codons were present in the region corresponding to env. The putative H18 gag gene (809 amino acids) had a sequence homologous to the N-terminal half of the mouse mammary tumor virus gag gene and locally to the Rous sarcoma virus gag gene. The putative H18 pol gene (900 residues) was homologous to the Rous sarcoma virus pol gene almost throughout the entire region. Two conserved regions among the retrovirus pol genes have been reported. One presumably corresponds to the DNA polymerase and the RNase H domain, and the other corresponds to the DNA endonuclease domain of the multifunctional protein pol. By the comparison of the deduced amino acid sequences of the putative endonuclease domain of six representative oncovirus genomes, a phylogenetic tree of the oncovirus genomes was constructed, and the intracisternal A-particle (type A) genome was found to be more closely related to the mouse mammary tumor virus (type B) and squirrel monkey retrovirus (type D) genomes.
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PMID:Nucleotide sequence of the Syrian hamster intracisternal A-particle gene: close evolutionary relationship of type A particle gene to types B and D oncovirus genes. 299 63

The human ribosomal RNA promoter contains two distinct control elements (UCE and core) both of which are recognized by the sequence-specific DNA binding protein UBF1, which has now been purified to apparent homogeneity. The purified factor activates RNA polymerase I (RNA pol I) transcription through direct interactions with either control element. A second RNA pol I transcription factor, designated SL1, participates in the promoter recognition process and is required to reconstitute transcription in vitro. Although SL1 alone has no sequence-specific DNA binding activity, deoxyribonuclease I footprinting experiments reveal that a cooperative interaction between UBF1 and SL1 leads to the formation of a new protein-DNA complex at the UCE and core elements. In vitro transcription experiments indicate that formation of the UBF1-SL1 complex is vital for transcriptional activation by UBF1. Thus, protein-protein interactions between UBF1 and SL1 are required for targeting of SL1 to cis-control sequences of the promoter.
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PMID:Functional cooperativity between transcription factors UBF1 and SL1 mediates human ribosomal RNA synthesis. 341 83

Immunoglobulin-binding factors are known to regulate the synthesis of B-cell-derived immunoglobulin heavy-chain isotypes. Cloning and nucleotide sequence determination of complementary DNA encoding rodent IgE-binding factors (IgE-BF) revealed that messenger RNA encodes a glycoprotein of 557 amino acids which is expressed as a precursor of relative molecular mass (Mr) 60,000 (60K) in COS7 monkey cells. We report here that the 3' two-thirds of the IgE-BF coding sequence shows a surprising homology (72%) at the DNA level with coding sequences of the gag and pol (DNA endonuclease) genes of the Syrian hamster intracisternal A particle (IAP H18), an endogenous retrovirus. This marked homology demonstrates that the rodent gene encoding IgE-BF is a hybrid gene which evolved very recently by integrating genes of viral origin, and that the encoded polypeptide comprises three separate domains: an IgE-BF domain and retrovirus-derived gag and DNA endonuclease-like domains. This may represent the first report of a cellular gene containing a virus-derived coding sequence.
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PMID:Retroviral gag and DNA endonuclease coding sequences in IgE-binding factor gene. 387 75

Reverse transcriptase from avian retrovirus has a physically associated DNA endonuclease with novel substrate and cofactor requirements. A similar endonuclease activity copurifies with pp32, a protein from viral cores that has been identified with the non-alpha region of the beta subunit of reverse transcriptase. Several temperature-sensitive mutants of avian retrovirus with thermolabile DNA polymerase were tested for thermal sensitivity of their DNA endonuclease activity. Two pol mutants of Rous sarcoma virus, ts335 and ts337, had thermolabile DNA endonuclease; a temperature-resistant revertant of ts335 had a heat-stable DNA endonuclease. DNA endonuclease is therefore a product of the pol gene and an integral part of the reverse transcriptase. A second class of pol mutants, typified by ts568 and ts553, had thermolabile DNA polymerase, but heat-stable DNA endonuclease.
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PMID:Virus-coded DNA endonuclease from avian retrovirus. 616 35

The interactions of calf thymus DNA polymerase alpha (pol alpha) with primer/templates were examined. Simply changing the primer from DNA to RNA had little effect on primer/template binding or dNTP polymerization (Km, Vmax and processivity). Surprisingly, however, adding a 5'-triphosphate to the primer greatly changed its interactions with pol alpha (binding, Vmax and Km and processivity). While changing the primer from DNA to RNA greatly altered the abilit of pol alpha to discriminate against nucleotide analogs, it did not compromise the ability of pol alpha to discriminate against non-cognate dNTPs. Thus the nature of the primer appears to affect 'sugar fidelity', without altering 'base fidelity'. DNase protection assays showed that pol alpha strongly protected 9 nt of the primer strand, 13 nt of the duplex template strand and 14 nt of the single-stranded template from hydrolysis by DNase I and weakly protected several bases outside this core region. This large DNA binding domain may account for the ability of a 5'-triphosphate on RNA primers to alter the catalytic properties of pol alpha.
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PMID:Interactions of calf thymus DNA polymerase alpha with primer/templates. 747 73


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