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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The DNA of wild-type Streptomyces lividans 66 is degraded during electrophoresis in buffers containing traces of ferrous iron. S. lividans ZX1, a mutant selected for resistance to DNA degradation, simultaneously became sensitive to phi HAU3, a wide-host-range temperate bacteriophage. A DNA fragment conferring phi HAU3 resistance was cloned; it contains a phage resistance gene whose deduced amino acid sequence is similar to the phage lambda Ea59 endonuclease. The S. lividans phi HAU3 resistance does not seem to be a classical restriction-modification system, because no host-modified phages able to propagate on the wild-type strain could be isolated. The cloned fragment did not make the host DNA prone to degradation during electrophoresis, indicating that the two phenotypes are controlled by different genes which were deleted together from the chromosome of ZX1.
Mol Microbiol 1994 Jun
PMID:Streptomyces lividans 66 contains a gene for phage resistance which is similar to the phage lambda ea59 endonuclease gene. 805 30

High-resolution S1 nuclease mapping of mRNA synthesised in vivo, in vitro run-off transcription with RNA polymerase from Streptomyces lividans and gene fusions were used to analyse the transcriptional organization of the SalI restriction-modification system of Streptomyces albus G. The salIR and salIM genes that encode the restriction endonuclease and its cognate methyltransferase constitute an operon which is mainly transcribed from sal-pR1, a promoter located immediately upstream of salIR, with two possible minor promoters further upstream. Another promoter, sal-pM, is within the 3' end of the salIR coding region, and allows expression of the modification gene in the absence of sal-pR1. The sal-pM promoter might be involved in the establishment of modification prior to restriction endonuclease activity. Sequences upstream of the apparent transcriptional start sites for sal-pR1 and sal-pM show similarity with the -10 region of typical vegetatively expressed eubacterial promoters, but appropriately centered -35 regions are absent.
Mol Microbiol 1993 Apr
PMID:Complex transcription of an operon encoding the SalI restriction-modification system of Streptomyces albus G. 831 78

The genetic determinant for pyocin AP41, a bacteriocin produced by Pseudomonas aeruginosa, has been cloned. The determinant is located on the chromosome flanked by a pair of inverted repeats, forming a transposon-like structure (TnAP41). TnAP41 possesses some features characteristic of the Tn3 family of transposons. Based on a comparison with the structure of the corresponding region of the chromosome of a non-producer strain, we propose that P. aeruginosa has acquired pyocinogeny by the transposition of TnAP41 into the chromosome. The determinant comprises two ORFs encoding the protein subunits responsible for the killing action (the large component) and immunity (the small component). Amino acid sequences of the C-terminus of the large component (the deoxyribonuclease domain) and the immunity protein show remarkable homology to those of E2 group colicins, suggesting that these bacteriocins, which are produced by distantly related species, have originated from a common ancestor.
Mol Gen Genet 1993 Feb
PMID:A novel transposon-like structure carries the genes for pyocin AP41, a Pseudomonas aeruginosa bacteriocin with a DNase domain homology to E2 group colicins. 838 91

Bis(1,10-phenanthroline)-copper(I) ion (OP2Cu+) binds reversibly to B-DNA and makes single-stranded cuts by oxidative attack on the deoxyribose moiety. The deoxyribonuclease activity is sequence-dependent yet not nucleotide-specific at the cutting site. OP2Cu+ sequence specificity was analysed in terms of local variations of DNA stability. Kinetic constants of strand cleavage were measured at sequence positions on the two strands and converted into activation free energies of the cleavage reaction. DNA unwinding free energies were calculated from the base sequence using B-DNA stacking parameters for calculations. The two free-energy variations were statistically compared for a series of DNA restriction fragments bearing the binding sites of regulatory proteins and representing a total of 345 DNA base positions. This study shows that the mean activation free energy of strand cleavage at a pair of opposing sugars across the DNA minor groove varies like the unwinding free energy of the DNA sequence delimited by opposing sugars (3 to 4 bp). A statistical equality between the two free-energy variations is demonstrated when considering the sum of the two cleavage events at the opposing sugars. Systematic deviations between the two free-energy distributions were observed at specific sequences, including polypurine-polypyrimidine tracts (AnTm/AmTn, CnTmCp/GpAmGn), alternating purine-pyrimidine tracts ((TA)n/(TA)n, (TG)n/(CA)n) and at certain G+C-rich triplets (GGC, GCC and CGC). The physical significance of these observations is discussed and a model of OP2Cu+ binding and cleavage specificity based on the free-energy equality is proposed.
J Mol Biol 1996 Jul 26
PMID:DNA-stacking interactions determine the sequence specificity of the deoxyribonuclease activity of 1,10-phenanthroline-copper ion. 875 18

The ATP-dependent deoxyribonuclease enzyme complex (AddAB) of Bacillus subtilis possesses two consensus ATP-binding sequences, located in the N-terminal region of both subunits. The highly conserved lysine residues in both consensus ATP-binding sequences were replaced by glycine, resulting in the mutant enzyme complexes AddAB-A-K36G (AddA*B) and AddAB-B-K14G (AddAB*). The mutation in subunit AddA reduced DNA repair and chromosomal transformation, and abolished bacteriophage PBS1-mediated transduction. This mutation also resulted in a complete loss of the ATP-dependent exonuclease and helicase activity. In contrast, the mutation in subunit AddB had only marginal effects. The recF and addAB genes are not required for transformation with plasmid DNA, but have overlapping activities in transformation with chromosomal DNA. By contrast to RecF, the AddAB enzyme is essential for PBS1-mediated transduction. However, recF has a more important function with respect to DNA repair than addAB.
Mol Microbiol 1996 Sep
PMID:Replacement of the lysine residue in the consensus ATP-binding sequence of the AddA subunit of AddAB drastically affects chromosomal recombination in transformation and transduction of Bacillus subtilis. 888 69

A novel enzymatic activity on nucleic acids was discovered in both muscle type (MT) and erythrocyte or common type (CT) isoforms of acylphosphatase, an enzyme that was previously known as a hydrolase (E.C.3.6.1.7). Both deoxyribonucleic and ribonucleic hydrolitic activity were assayed on a variety of substrates. Our results demonstrate that acylphosphatase possesses both Mg++ dependent deoxyribonuclease and ribonuclease activities, at pH ranging from 5.0 to 6.8. Furthermore, we present evidences, for both isoenzymatic forms, of the coexistence of exonucleolytic and endonucleolytic activities on DNA.
Biochem Mol Biol Int 1996 Sep
PMID:Characterization of a novel nucleolytic activity of acylphosphatases. 888 72

We have established a stably transformed human neuroblastoma cell line (MC65) that conditionally expresses a C-terminal derivative of the amyloid beta protein precursor (beta PP) termed S beta C (a fusion protein composed of the amino-17 and carboxyl-99 residues of beta PP). Conditional expression of S beta C (mediated by the withdrawal of tetracycline from the culture medium) induces pronounced nuclear DNA fragmentation and cytotoxicity in this cell line. These effects are enhanced by hyperoxygen and suppressed by hypooxygen and antioxidants. This cell line is relatively insensitive to the extracellular application of amyloid beta 25-35, and coculture experiments suggest that this cytotoxicity is mediated by an intracellular process. These findings suggest that the overexpression of the C-terminal domain of beta PP can disrupt normal cellular processes in these cells in such a way as to induce a directed (deoxyribonuclease-mediated) mechanism of cell death. This process appears to be modulated and/or mediated by a reactive oxygen specie(s) (ROS). Consistent with a role for ROS in the process of S beta C-mediated toxicity, we have found that the MC65 cell line is hypersensitive to oxidative stress and that it is this sensitivity that appears (at least in part) to underlie its susceptibility to S beta C.
Mol Chem Neuropathol
PMID:Neurodegenerative mechanisms in Alzheimer disease. A role for oxidative damage in amyloid beta protein precursor-mediated cell death. 897 93

Type I restriction-modification systems bind to non-palindromic, bipartite recognition sequences. Although these enzymes methylate specific adenine residues within their recognition sequences, they cut DNA at sites up to several thousand base-pairs away. We have investigated the mechanism of how EcoR124II, a type IC restriction-modification system, selects the cleavage site. Restriction studies with different DNA constructs revealed that circular DNA requires only one non-methylated recognition sequence to be cut, whereas linear DNA needs at least two such sites. Cleavage of linear DNA is independent of site orientation. Further investigations of the linear substrates revealed a mechanism whereby the double-strand break is introduced between two recognition sequences. We propose a model for the selection of restriction sites by type I enzymes where two EcoR124II complexes bind to two recognition sequences. Lack of methylation at a site stimulates the enzyme to translocate DNA on both sides of the recognition sequence. Thus the two complexes approach each other and, at the point where they meet, they interact to introduce a double-strand break in the DNA.
J Mol Biol 1996 Dec 13
PMID:DNA cleavage by the type IC restriction-modification enzyme EcoR124II. 898 Jun 81

The salIR and salIM genes encode the endonuclease and methyltransferase components of the SalI restriction-modification system from Streptomyces albus G. Expression of the salI genes in Escherichia coli was investigated and major differences with Streptomyces were found. In E. coli there is no detectable expression of the salI R gene due to inactivity of the sal-pR promoter region. In the natural host of the system this region directs transcription of the salI genes as a bicistronic message. In contrast to salIR, salIM is transcribed in the heterologous host from a promoter within the salI DNA. Since sal-pR is not active, the gene cannot be expressed as part of the salI operon. It is probably transcribed from sal-pM, a promoter internal to the operon which allows independent expression of the modification gene in Streptomyces. Replacement of sal-pR by the strong pLac promoter allows expression of salIR in E. coli and enhances expression of salIM. The resulting strain produces about 10 times more endonuclease than a Streptomyces clone containing the SalI system under the control of sal-pR.
Mol Gen Genet 1996 Nov 27
PMID:Comparative analysis of expression of the SalI restriction-modification system in Escherichia coli and Streptomyces. 900 89

To evaluate the specificity and applicability to the study of human tumor cells of the reverse transcription (RT) in situ PCR and RT polymerase chain reaction (PCR) in situ hybridization techniques, we examined five melanoma cell lines and five nonmelanoma lines for tyrosinase mRNA using primers specific for tyrosinase. Each procedural step was optimized and minutely controlled, and results from the in situ techniques and solution-phase RT-PCR were compared. All melanoma lines showed a specific pattern of perinuclear cytoplasmic reaction not seen in nonmelanoma lines. There was exact agreement between the results from the RT in situ PCR and RT-PCR in situ hybridization techniques and those from solution-phase RT-PCR. Ribonuclease digestion abolished cytoplasmic staining, as did omission of the reverse transcriptase step. Nuclear staining was seen in melanoma and nonmelanoma lines, apparently as a result of DNA synthesis from repair-replication and mispriming or nonspecific amplification. Neither high concentrations of deoxyribonuclease nor long incubation periods abolished this effect completely. Demonstration of cytoplasmic mRNA by RT in situ PCR and RT-PCR in situ hybridization specifically identifies cells of melanocytic lineage.
Diagn Mol Pathol 1997 Feb
PMID:Demonstration of cytoplasmic tyrosinase mRNA in tissue-cultured cells by reverse transcription (RT) in situ polymerase chain reaction (PCR) and RT PCR in situ hybridization. 902 34


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