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

DNA of the IS-elements IS1 and IS2 was prepared by digestion of appropriate heteroduplex molecules with endonuclease S1, followed by sucrose gradient centrifugation or gel electrophoresis. The material obtained is homogeneous with regard to size. The length of IS1 DNA is 820 +/- 65 nucleotides, the length of IS2 DNA is 1,350 +/- 70 nucleotides. IS1 DNA is not cleaved by the restriction endonucleases Eco R1, Hind II or Hind III. IS2 DNA is cleaved once by each of the two latter enzymes. The buoyand density determined by equilibrium centrifugation of Hg-complexes in Cs2so4 corresponds to a GC content of approximately 50%. Labelling with polynucleotide kinase indicates that both IS DNA's have a guanosyl residue at both of their 5'-termini.
Mol Gen Genet 1976 May 07
PMID:The isolation of IS1 and IS2 DNA. 93 52

The DNA sequence IS1, which is 800 pairs long, has been shown to integrate into various bacterial and phage operons. The presence of this DNA sequence in the gal operon of E. coli K12 leads to an 30-2000 fold increase in deletion formation in the gal region as compared to wildtype. This high frequency of deletion formation is specific for IS1 and is independent of the cellular recA function. While the frequency of reversion of gal::IS1 mutations, which also is independent of recA, is not affected by the growth temperature of the cells, the formation of deletions in the gal::IS1 system is strongly dependent on the temperature of growth. Mapping experiments showed that one endpoint of the deletions in most cases is at the site of the IS1 mutation and the second endpoint seems to be at various but preferred sites. The formation of the different classes of delections observed is affected differently by the growth temperature of the cells. A model to account for these results is presented.
Mol Gen Genet 1975
PMID:IS1 is involved in deletion formation in the gal region of E. coli K12. 110 Oct 28

When Escherichia coli HB101 harbors pWR127, a plasmid comprising the viaB gene from Citrobacter freundii WR7004 and the ColE1-derived pACKC1, the strain produces the virulence (Vi) antigen. Vi antigen expression is abolished (Vi- phenotype), however, when an IS1 or IS1-like DNA element inserts into the viaB region. To determine the sites of IS1 insertion, pWR127 DNAs extracted from 95 independently isolated Vi- strains were analyzed by digestion with the restriction endonuclease PstI and agarose gel electrophoresis. Ten insertion sites were found distributed non-randomly in an area of about 1.3 kb. Nine Vi+ strains (two Citrobacter, two E. coli, and five Salmonella strains), four of which contain pWR127, were then tested for the presence of IS1 by DNA-DNA hybridization. Of the nine strains, five were stable Vi+ and did not contain IS1. The other four which generated Vi- strains, contained IS1. When pRR134, a plasmid that contains IS1 was transferred into a stable Vi+ Salmonella typhimurium strain carrying pWR127 (OU5140), Vi- strains were produced from which pWR127 derivatives carrying IS1 inserts could be isolated. It appears, therefore, that the presence of an IS1 or IS1-like element in a strain is required for conversion of the Vi+ expression state to the Vi- expression state.
Mol Gen Genet 1992 Aug
PMID:Role of IS1 in the conversion of virulence (Vi) antigen expression in Enterobacteriaceae. 132 99

The transposase encoded by insertion sequence IS1 is produced from two out-of-phase reading frames (insA and B'-insB) by translational frameshifting, which occurs within a run of six adenines in the -1 direction. To determine the sequence essential for frameshifting, substitution mutations were introduced within the region containing the run of adenines and were examined for their effects on frameshifting. Substitutions at each of three (2nd, 3rd and 4th) adenine residues in the run, which are recognized by tRNA(Lys) reading insA, caused serious defects in frameshifting, showing that the three adenine residues are essential for frameshifting. The effects of substitution mutations introduced in the region flanking the run of adenines and in the secondary structures located downstream were, however, small, indicating that such a region and structures are not essential for frameshifting. Deletion of a region containing the termination codon of insA caused a decrease in beta-galactosidase activity specified by the lacZ fusion plasmid in frame with B'-insB. Exchange of the wild-type termination codon of insA for a different one or introduction of an additional termination codon in the region upstream of the native termination codon caused an increase in beta-galactosidase activity, indicating that the termination codon in insA affects the efficiency of frameshifting.
Mol Gen Genet 1992 Nov
PMID:DNA sequences required for translational frameshifting in production of the transposase encoded by IS1. 133 30

A second-site mutation that restored DNA binding to ADR1 mutants altered at different positions in the two zinc fingers was identified. This mutation (called IS1) was a conservative change of arginine 91 to lysine in a region amino terminal to the two zinc fingers and known from previous experiments to be necessary for DNA binding. IS1 increased binding to the UAS1 sequence two- to sevenfold for various ADR1 mutants and twofold for wild-type ADR1. The change of arginine 91 to glycine decreased binding twofold, suggesting that this arginine is involved in DNA binding in the wild-type protein. The increase in binding by IS1 did not involve protein-protein interactions between the two ADR1 monomers, nor did it require the presence of the sequences flanking UAS1. However, the effect of IS1 was influenced by the sequence of the first finger, suggesting that interactions between the region amino terminal to the fingers and the fingers themselves could exist. A model for the role of the amino-terminal region based on these results and sequence homologies with other DNA-binding motifs is proposed.
Mol Cell Biol 1992 Dec
PMID:A mutation outside the two zinc fingers of ADR1 can suppress defects in either finger. 144 3

The DNA nucleotide sequence from the central region of the composite transposons Tn9* and Tn9' at the junction with the right copy of IS1 was determined. From the data obtained it follows that both transposons are members of the Tn9 family, although they contain additional DNA segments with regard to Tn9 of the length about 320 and 290 b.p. respectively lying distal to the cat gene. It was proposed that all the transposons of the Tn9 family have been formed as a result of IS1-mediated deletions of the plasmid R100 r-determinant. It was revealed from the data of computer analysis that in the sequenced DNA there are two potential promotors with transcription directed opposite in relation to the transcription of the cat gene.
Mol Biol (Mosk)
PMID:[Primary structure of two natural IS1-flanking transposons Tn9* and Tn9' coding for stability to chloramphenicol]. 165 20

The plasmid-transposon Tn9-322 was constructed by inverted transposition from the pBR322::Tn9 plasmid. The precise excision of the Tn9-322 transposon from the proB gene site can proceed by the Campbell's model. This fact was demonstrated by appearance of the plasmid-transposons after their precise excision. They contain two IS1 elements flanking a short direct repeat of the target DNA. The recombinational mechanism of precise excision of Tn9 type transposons seems not to be alternative but looks as an additional one to a well-known slippage mechanism proved for Tn5 and Tn10.
Mol Biol (Mosk)
PMID:[Evidence for Campbell's mechanism for fine excision of Tn9 type transposons in Escherichia coli K12]. 165 17

To facilitate efficient allelic exchange of genetic information into a wild-type strain background, we improved upon and merged approaches using a temperature-sensitive plasmid and a counter-selectable marker in the chromosome. We first constructed intermediate strains of Escherichia coli K12 in which we replaced wild-type chromosomal sequences, at either the fimB-A or lacZ-A loci, with a newly constituted DNA cassette. The cassette consists of the sacB gene from Bacillus subtilis and the neomycin (kanamycin) resistance gene of Tn5, but, unlike another similar cassette, it lacks IS1 sequences. We found that sucrose sensitivity was highly dependent on incubation temperature and sodium chloride concentration. The DNA to be exchanged into the chromosome was first cloned into derivatives of plasmid pMAK705, a temperature-sensitive pSC101 replicon. The exchanges were carried out in two steps, first selecting for plasmid integration by standard techniques. In the second step, we grew the plasmid integrates under non-selective conditions at 42 degrees C, and then in the presence of sucrose at 30 degrees C, allowing positive selection for both plasmid excision and curing. Despite marked locus-specific strain differences in sucrose sensitivity and in the growth retardation due to the integrated plasmids, the protocol permitted highly efficient exchange of cloned DNA into either the fim or lac chromosomal loci. This procedure should allow the exchange of any DNA segment, in addition to the original or mutant allelic DNA, into any non-essential parts of the E. coli chromosome.
Mol Microbiol 1991 Jun
PMID:Allelic exchange in Escherichia coli using the Bacillus subtilis sacB gene and a temperature-sensitive pSC101 replicon. 168 93

TraJ and SfrA are, respectively, plasmid and host (Escherichia coli)-encoded proteins normally required for F plasmid traY promoter function. Beginning with plasmids in which a traY-lacZ fusion gene, designated phi (traY'-'lacZ)hyb, and lacY are expressed from the F plasmid traY promoter, we isolated mutants in which lac gene expression was SfrA or TraJ-independent. A total of 45 of 50 SfrA-independent isolates obtained after 2-aminopurine mutagenesis proved to have chromosomal mutations, whereas four out of four isolates obtained without mutagenesis had plasmid mutations. All of 17 isolates selected for TraJ-independent expression after mutagenesis had plasmid mutations. By restriction endonuclease digestions, 25 of 26 SfrA-independent and TraJ-independent plasmid mutations were insertions. Four of the former and three of the latter were examined further. By sequence analysis, all seven proved to be IS1 or IS2 insertions defining five insertion sites between base-pairs -49 and -82 with respect to the major traY transcription initiation site. In two cases, the same insertion allele was obtained from the two selection schemes. All three of the mutants selected for TraJ-independent gene expression manifested SfrA-independent expression as well, and levels of beta-galactosidase in different plasmid mutant strains lacking TraJ and SfrA were indistinguishable. By primer extension analysis, transcription initiation sites for traY mRNA synthesis were unaltered by the mutations. Replacing the tra sequence upstream from base-pair -78, without genetic selection, increased beta-galactosidase activity in the absence of TraJ and SfrA greater than tenfold. Activity increased two- to threefold more in a traJ+ sfrA mutant strain, and fivefold more in a traJ+ sfrA+ strain. Activity was unaltered in an sfrA+ strain without TraJ. By primer extension analysis, the traY promoter was utilized under all conditions. The data indicate that regulation of traY promoter activity is strongly dependent on sequence context.
J Mol Biol 1991 Jul 20
PMID:Regulation of the F plasmid traY promoter in Escherichia coli K12 as a function of sequence context. 190 41

The IS 1-encoded protein InsA binds specifically to both ends of IS1, and acts as a repressor of IS1 gene expression and may be a direct inhibitor of the transposition process. We show here, using DNasel 'foot-printing' and gel retardation, that the InsA binding sites are located within the 24/25 bp minimal active ends of IS1 and that InsA induces DNA bending upon binding. Conformational modification of the ends of IS1 as a result of binding of the host protein integration host factor (IHF) to its site within the minimal ends has been previously observed. Using a collection of synthetic mutant ends we have mapped some of the nucleotide sequence requirements for InsA binding and for transposition activity. We show that sequences necessary for InsA binding are also essential for transposition activity. We demonstrate that InsA and IHF binding sites overlap since some sequence determinants are shared by both InsA and IHF. The data suggest that these ends contain two functional domains: one for binding of InsA and IHF, and the other for transposition activity. A third region, when present, may enhance transposition activity with an intact right end. This 'architecture' of the ends of IS1 is remarkably similar to that of IS elements IS10, IS50 and IS903.
Mol Microbiol 1990 Sep
PMID:Functional organization of the ends of IS1: specific binding site for an IS 1-encoded protein. 196 38


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