Close vicinity of IS1 integration sites in the leader sequence of the gal operon of E. coli

Kühn, S.; Fritz, Hans-Joachim; Starlinger, Peter

doi:10.1007/bf00267414

Cited by 96 publications

(25 citation statements)

References 23 publications

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“…The gel slice was then melted by heating it to 65°C and was loaded on a second 1% lowmelting-point agarose gel. The micronuclear DNA was again excised, digested in situ with the appropriate restriction enzyme when required, and purified from the gel as described by Kuhn et al (35).…”

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confidence: 99%

Micronuclear genome organization in Euplotes crassus: a transposonlike element is removed during macronuclear development.

Baird¹,

Fino²,

Tausta³

et al. 1989

Mol. Cell. Biol.

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After mating, hypotrichous ciliated protozoa transform a set of their micronuclear chromosomes into thousands of short, linear DNA molecules that form the macronuclear genome. To examine micronuclear genome organization in the hypotrich Euplotes crassus, we have analyzed two cloned segments of micronuclear DNA as well as the macronuclear DNA molecules that are derived from them. E. crassus was found to display a number of features characteristic of other hypotrich genomes, including (i) clustering and close spacing of the precursors of macronuclear DNA molecules, (ii) the frequent occurrence of internal eliminated sequences within macronuclear precursors, (iii) overlapping macronuclear precursors, (iv) lack of telomeric repeats at the ends of macronuclear precursors, and (v) alternative processing of the micronuclear chromosome to yield multiple macronuclear DNA molecules. In addition, a moderately repetitive, transposonlike element that interrupts the precursors of two macronuclear DNA molecules has been identified and characterized. This transposonlike element, designated Tecl, is shown to be reproducibly removed from one of the macronuclear precursors during independent episodes of macronuclear development.Hypotrichous ciliated protozoa undergo an extensive genome reorganization process during their life cycles (for reviews, see references 32 and 47). The ability of these unicellular organisms to drastically alter their genome yet maintain genetic continuity stems from the fact that each cell contains two distinct nuclei. The micronucleus, which contains chromosome-sized DNA, is transcriptionally inactive but plays a major role during the sexual phase of the life cycle and is often referred to as the germ line nucleus. In contrast, the macronucleus is responsible for all nuclear transcription during vegetative growth and is equivalent to a somatic nucleus. The macronuclear genome is unusual in that it is composed of 10,000 to 20,000 different short, linear, gene-sized DNA molecules with an average size of approximately 2 kilobase pairs (kbp). There are generally 1,000 or more copies of each linear DNA molecule per macronucleus, and each appears to be an independent genetic unit which contains the information required to encode and express a single gene product (20,27) as well as to allow its own replication.Despite its unusual genetic organization, the macronucleus replicates and divides during each vegetative cell cycle. However, after the sexual phase of the life cycle, the macronucleus is destroyed and a new one is generated from a mitotic copy of the micronucleus. It is during this process of macronuclear development that extensive genomic changes occur, giving rise to the unique genetic organization of the macronucleus. At the cytological level, macronuclear development begins with the replication of the micronuclear chromosomes to form polytene chromosomes. The occurs, resulting in the loss of up to 95% of the sequence complexity of the micronuclear genome. The vesicles then break down, and the remain...

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confidence: 99%

Micronuclear genome organization in Euplotes crassus: a transposonlike element is removed during macronuclear development.

Baird¹,

Fino²,

Tausta³

et al. 1989

Mol. Cell. Biol.

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“…In the latter case, the virus is not required to integrate near the 5' end of the gene and can integrate some distance away (23)(24)(25)27). Inactivation of a gene by a transposable element is most easily understood when the integration is within the transcriptional unit (8,13,17,28,31). Nevertheless, inactivation of gene expression has been seen by integration of transposable elements external to the known transcriptional and regulatory boundaries of some genes (19,20).…”

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confidence: 99%

Dilute-coat-color locus of mice: nucleotide sequence analysis of the d+2J and d+Ha revertant alleles.

Hutchison¹,

Copeland²,

Jenkins³

1984

Mol. Cell. Biol.

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The unstable dilute-coat-color mutation (d) of DBA/2J mice has been shown to be the result of integration of an ecotropic murine leukemia virus within the mouse genome. Molecular cloning and restriction enzyme analysis of the dilute allele and the viral preintegration site (+ allele), as wel as two independent dilute revertants (d+2J and d+Ha), suggested that reversion is due to virus excision occurring by homologous recombination involving the viral long terminal repeats. The DNA sequence has now been determined for the cell-virus junctions of the provirus associated with the d mutation, for the viral preintegration site, and for the two revertant sites. These data (i) (6,16,21,(22)(23)(24)(25)(26)(27), and is generally regarded as the causative event for tumor induction by retroviruses. Activation can occur either directly, by utilizing the promoter sequences of the viral long terminal repeat (LTR), or indirectly, by using LTR enhancer sequences. In the latter case, the virus is not required to integrate near the 5' end of the gene and can integrate some distance away (23)(24)(25)27). Inactivation of a gene by a transposable element is most easily understood when the integration is within the transcriptional unit (8,13,17,28,31). Nevertheless, inactivation of gene expression has been seen by integration of transposable elements external to the known transcriptional and regulatory boundaries of some genes (19,20).Germline integration of retroviruses in mice has caused at least two mutations (3, 10, 11). The integration of a Moloney murine leukemia virus (Mo-MuLV) at the Mov-13 locus resulted in a recessive lethal mutation (10). In this case, the virus induced the mutation by integrating into the first intron of the al(I) collagen gene (4) Fig. 1. Single-stranded template DNA was purified and the sequence reactions were carried out as described in the Bethesda Research Laboratories Cloning/Sequencing kit instruction manual. DNA se-

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“…Where restriction map ambiguities existed, restriction fragments were either purified from agarose gels by phenol extraction, then cut with a second enzyme (20) and the products examined by gel electrophoresis, or the restriction fragment was digested directly in the gel with a second enzyme before re-electrophoresis (21). Crossedcontact hybridization experiments (see below) also helped resolve restriction maps.…”

Section: Methodsmentioning

confidence: 99%

Characterization of Rabbit Genes for Synovial Cell Collagenase

Fini

Gross

Brinckerhoff

1986

Arthritis & Rheumatism

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To provide tools for understanding collagenase gene expression in rheumatoid arthritis, we have isolated and characterized genomic clones for rabbit synovial cell collagenase. These clones represent 2 types of collagenase gene, at least 1 of which is transcribed in synovial fibroblasts. By examining the rabbit genome in situ, we provide evidence that there are only 2 different synovial cell collagenase genes found in a haploid genome. Amplification of these genes is not a mechanism far collagenase messenger RNA induction by phorbol esters.The metalloproteinase, collagenase, plays a primary role in the joint destruction seen in rheumatoid arthritis (1). Vast excesses of this enzyme are secreted by the fibroblasts of the rheumatoid pannus. The fact that collagen breakdown can be initiated only by collagenase makes this enzyme rate-limiting in collagenolysis. One approach to the successful control of collagenolysis in diseases such as rheumatoid arthritis may lie in inhibiting the production of collagenase. Thus, an understanding of mechanisms regulating Studies in our laboratory, designed to understand the control of collagenase secretion, have been facilitated by the development of a cell culture system of synovial fibroblasts from rabbits (2). These cultures secrete negligible levels of collagenase when untreated. However, they can be stimulated to secrete major amounts of collagenase by treatment with numerous agents, including the tumor promoter, phorbol myristate acetate (PMA) (3), and crystals of monosodium urate monohydrate (4). Furthermore, additional agents such as retinoic acid or dexamethasone can reverse or suppress induction (5). To date, experiments with human synovial cells have corroborated our findings with the rabbit cell studies, and have thus validated the rabbit system as a model (6,7).Earlier studies demonstrated that inducers act to increase the synthesis of new collagenase protein rather than stimulate the release of previously synthesized enzyme stored intracellularly (8). With the development of a complementary DNA (cDNA) clone for collagenase, we showed that on induction, an increase in immunoreactive collagenase secreted into the culture medium is directly correlated with increased collagenase messenger RNA (mRNA) levels (9). Several steps in RNA metabolism could contribute to the increase in collagenase message levels, including increased transcription from the collagenase gene(s), greater mRNA stability, or changes in processing of pre-mRNA to mRNA. To study the contribution of these processes to mRNA induction, as well as the mechanisms by which they operate, requires more than a cDNA clone, which is merely a copy of mRNA. The collagenase gene itself must be isolated

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Close vicinity of IS1 integration sites in the leader sequence of the gal operon of E. coli

Cited by 96 publications

References 23 publications

Micronuclear genome organization in Euplotes crassus: a transposonlike element is removed during macronuclear development.

Micronuclear genome organization in Euplotes crassus: a transposonlike element is removed during macronuclear development.

Dilute-coat-color locus of mice: nucleotide sequence analysis of the d+2J and d+Ha revertant alleles.

Characterization of Rabbit Genes for Synovial Cell Collagenase

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