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

The involvement of the transposable DNA element of E. coli K12 chromosome in integrative recombination of RP1 plasmid was studied. Using temperature sensitive for replication plasmid RP1ts12--the derivative of RP1 which contains mutated transposon Tnl, it was shown that integration of RP1 into host chromosome and Hfr formation may occur according to a mechanism mediated by chromosome IS-elements. Plasmids that are desintegrated from the chromosome of these Hfrs contain discrete DNA segments (IS-elements) and possess elevated frequency of integration into chromosome of rec+ cells. The latter was used for selection of RP1ts12 recombinants carrying chromosome IS. For identification of IS involved in RP1 integration the number of independent RP1ts 12 recombinants was subjected to restriction and heteroduplex analysis. By analysing recombinants integrated into bacterial chromosome with frequency 5 X 10(-3), a new IS-element of E. coli K12 designated IS111 was discovered. IS111-element is about 1500bp of length, contains Smal, Pst1 and BamH1 restriction endonuclease sites and was found in the same position on the plasmid RP1 in two different orientations. IS-elements that have been revealed in a number of other RP1ts12 recombinants were preliminary identified as IS1-like elements. One recombinants plasmid was found to have an IS5-like elements. The activity of IS-elements inserted into RP1ts12 in recA-dependent integrative recombination was estimated. From the data of absolute and relative RP1ts12 integration frequencies mediated by IS111, IS1- and IS5-like elements a conclusion was made about the absence of E. coli K12 chromosome IS-elements in RP1 plasmid. The Hfr-formation and chromosomal gene transfer by recombinant plasmids RP1ts12: IS111 were studied. The possibility to use insertion RP1ts12 derivatives for the estimation of copies number, mapping and definition of orientation of IS-elements in bacterial chromosome and the possibilities for detection of transposable DNA elements using RP1ts12 in a wide range of gram-negative bacteria are discussed.
Mol Biol (Mosk)
PMID:[Thermosensitive vector derived from RP1 plasmid for detection of transposable elements]. 628 85

The regulatory region of the ompA gene from Escherichia coli has been characterized by biochemical and genetic approaches. Two overlapping promoters, P1 and P2, organized in that order with respect to the ompA coding sequence, were identified and it was found that ompA possesses an unusually long leader region. Both P1 and P2 were active in an in vitro transcription system although S1 mapping analysis of the ompA mRNA made in vivo showed that P2 was mainly responsible for transcription of the gene. Confirmation of this was obtained by studying down-promoter mutants of ompA cloned in pSC101. These mutants were classified into two groups, deletions and insertions. The deletions, which were caused by the IS102 insertion element found in pSC101 removed the--35 regions of both P1 and P2. However, since P2 was distally situated with respect to the IS element it was less extensively damaged and it is proposed that the residual P2 sequence is responsible for the low level of expression observed. In addition to an IS102 insertion in the promoter region four IS1 insertion mutants were characterized. These had integrated at different positions in the ompA leader region and were all incompletely polar.
Mol Gen Genet 1982
PMID:Characterisation of the promoters for the ompA gene which encodes a major outer membrane protein of Escherichia coli. 629 77

Transposable-element-mediated fusion of the conjugal plasmid pOX38::Tn9 with pBR322 results in the appearance of cointegrates composed of a single copy of each plasmid, and cointegrates which carry a single copy of pOX38 but multiple tandem copies of pBR322. These plasmids are separated by directly repeated copies of the transposable element. We demonstrate here that such multimers can be generated from monomeric cointegrates, probably by unequal crossing over between the flanking Tn9(IS1) elements. Their appearance is thus not necessarily associated with the original transposition (fusion) event. Our study demonstrates that the process of duplication is strongly dependent on the homologous recombination system of Escherichia coli, since it is undetectable by our methods in recA- strains. It is also strongly dependent on the presence of a functional DNA polymerase I in the cell. The major pathway(s) for this duplication thus appears to rely on both the homologous recombination system and the replication of the duplicated segment.
J Mol Biol 1983 Mar 25
PMID:IS1-mediated tandem duplication of plasmid pBR322. Dependence on recA and on DNA polymerase I. 630 80

The genomes of three plaque-forming recombinant phages between phage P1 and plasmid p15B were characterized by restriction cleavage analysis and electron microscopic heteroduplex studies. The structure of all three P1-15 hybrid genomes differs from that of P1 DNA in the res mod region coding for restriction and modification systems EcoP15 and EcoP1, respectively. P1-15 hybrid 2 shows an additional major difference to P1 around the site of the residential IS1 element of P1 and it does not carry an IS1 in its genome.
J Mol Biol 1983 Mar 25
PMID:Physical analysis of the genomes of hybrid phages between phage P1 and plasmid p15B. 630 82

Deleted derivatives of F lac+ proC+ tsx+/- purE+ plasmids ORF203 and F13 were isolated and physically characterized. Among 31 deletions, 24 were adjacent to the gamma delta element on F, four were associated with IS2 or IS3 elements normally present on F, and three displayed additional DNA rearrangements. With the genetic selection employed, the deletion endpoints in the chromosomal segment could fall anywhere within a 210 kb (5 min) region between proC and lac. The distribution of endpoints in this region was not random: the endpoints primarily occurred in an extended region near purE, and a 50 kb segment between tsx and purE was devoid of deletion endpoints. Deletion termini for mutants obtained from F13, which contains an additional 48 kb-segment interposed between gamma delta and the target region on ORF203, displayed a distribution similar to that seen for ORF203. Among simple deletions, there was no marked tendency for the chromosomal deletion endpoints to fall at IS1, IS3, or IS5 elements normally present in this chromosomal region. Point mutations and mutations caused by gamma delta or IS transposition into lac appeared in a small proportion of all plasmids studied.
Mol Gen Genet 1983
PMID:Gamma delta-mediated deletions of chromosomal segments on F-prime plasmids. 630 74

Total DNAs from twelve natural isolates of Escherichia coli from animals and humans were examined by hybridization with a probe for IS1. Considerable variation in copy number was found. In the case of two strains isolated from the same individual, one strain contained no copies of IS1 and the other, much greater than 30. Evidence was also obtained for the existence of IS1-like elements (iso-IS1s) of greater than 15% sequence divergence relative to the IS1 from antibiotic resistance plasmid R100.
Mol Gen Genet 1983
PMID:Distribution of insertion element IS1 in natural isolates of Escherichia coli. 630 98

We have studied the effect on the transposition activity of IS1 of the position and orientation of the element in the donor replicon. Previous studies have shown that the IS1s in the compound transposon Tn9 have different activities in forming plasmid cointegrates. In this study, designed to investigate the sources of this differential activity, we have cloned Tn9 (together with 132 base-pairs of flanking DNA) into several sites in pBR322 and created various derivatives of these plasmids to be used as donor molecules in plasmid fusion experiments. These pBR322-Tn9 plasmids were allowed to form cointegrates with a conjugative, F-derived plasmid, and a large collection of independently formed cointegrates was isolated. The relative activities of the two IS1 elements of Tn9 were estimated by examining the structures of the cointegrates for the frequency of usage of each of the IS1s in cointegrate formation. The results suggest that IS1 activity is modulated by the transcription activity of adjacent DNA sequences in the donor plasmids. Transcription directed into an IS1 inhibits its activity. Confirmatory evidence for this hypothesis is provided by the observation that deletion of adjacent promoters of transcription relieves the inhibitory effect on IS1 activity.
J Mol Biol 1983 Oct 15
PMID:Cointegrate formation mediated by Tn9. II. Activity of IS1 is modulated by external DNA sequences. 631 38

Presence of insertion element IS1 within an operon leads to absence of expression of genes distal to its integration site. This strong polar effect is observed irrespective of the orientation of IS1. Here I report on a mutant of E. coli K12 which allows turn-on of genes located distally to IS1. This turn-on is due to activation of transcription starting within IS1. The activation of transcription is under the control of a regulatory locus (sis1) which acts in trans. The regulatory locus itself changes its state, which leads to an alternating turn-off/turn-on of genes located distal to IS1: The rate of turn-off was observed with a frequency of about 0.3% (per cell and per generation), that of turn-on with a frequency of about 0.015% (per cell and per generation).
Mol Gen Genet 1983
PMID:A control system which causes alternating turn-off/turn-on of transcription on insertion element IS1. 631 12

Tn9, like other transposable elements, promotes formation of deletions. This activity has been monitored using a plasmid (pAA3B101) on which deletions can be selected positively as galactose-resistant colonies. Measurements of deletion formation by a series of internal deletions of Tn9, generated by restriction endonucleases, show that the two IS1 elements of Tn9 are functionally non-equivalent. IS1-L is active while IS1-R is inactive. The inactive IS1-R element can, however, be reactivated by a deletion which specifically removes the cat promoter. This result indicates that the inactivity of IS1-R is not due to an altered sequence (Galas & Chandler, 1982), but due to inhibition by transcription from the cat promoter (Machida et al., 1983) which acts in a direction opposite to IS1-R transcription. The occurrence of non-equivalent IS in all transposons analysed suggests that this may be an important feature of organization required for the stability of these composite elements.
J Mol Biol 1984 Mar 15
PMID:A deletion analysis of transposon Tn9. 632 21

The movement of the bacterial insertion sequence IS1 often generates cointegrate structures in which donor and target replicons are connected by direct repeats of IS1. The experiments reported here were designed to understand how IS1 transposition is controlled. Our physical characterization of the structures of cointegrates between an F factor ( pOX38 ) and a set of pBR322::Tn9-related plasmids indicate that the relative mobilities of the two IS1 elements of Tn9 are inversely correlated with the strength of promoters upstream in the vector DNA. This implies that transcription across the ends of an IS1 element inhibits its transposition. Transcriptional inhibition may be due to interference with either the synthesis or the action of transposase.
J Mol Biol 1984 Apr 05
PMID:Transcriptional control of IS1 transposition in Escherichia coli. 632 10


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