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D Charlier

Publications and source records attributed to D Charlier.

At least 55 records · Page 3Linked to original sources
PubMed1984

Acute myeloid leukemia with giant inclusions: cytochemical and ultrastructural study.

Giant granules formation was investigated in myeloblasts of a patient with acute myelogenous leukemia by means of the combined techniques of peroxidase cytochemistry both in light and electron microscopy. Several pathologic features were noted: first an abnormal packaging of peroxidase in the peripheral area in large azurophilic granulations, second the progressive enlargement of huge vacuolar inclusions resulting from the interaction and fusion of large azurophilic granules with each other, with normal-sized primary granules and with cytoplasmic components. Microcrystalline structure could not be found in giant vacuoles no in vacuolar inclusions resembling Auer bodies. This last finding could explain that no disseminated intravascular coagulation was observed in our patient.

Aged↗
PubMed1983

Turn-on of inactive genes by promoter recruitment in Escherichia coli: inverted repeats resulting in artificial divergent operons.

We have characterized two rearrangements consisting of inverted repeats of the argE gene. The promoters (p) of argE and of argCBH face each other over an internal operator. The rearrangements were obtained as reactivations of argE in a strain harboring an argEp deletion on a lambda darg prophage. In both cases the repeat included argE and argCBHp on either side of a unique sequence; the result is a divergent operon in which each copy of argCBHp reads into the adjacent argE repeat. In one case, the pair of repeats adjoins the silent parental gene, forming a triplication (comes from leads to comes from). The other rearrangement consists of a single argE palindrome, but the whole prophage is rearranged into an inverted repeat, analogous to certain lambda dv's. Both structures could be explained by breakage of a replication fork passing argE and by inaccurate rejoining of strands. The lambda dv-like rearrangement would result from breakage at both replication forks of a phage or prophage replicating during transient release of immunity. The triplication would imply breaking of a chromosomal replication fork, formation of a cyclic intermediate by recombination between the daughter duplex molecules and reinsertion into the parental argE gene. Formation of a triplication by replication errors involving appropriate strand switchings and branch migrations can not be excluded however.

Bacteriophage lambda↗
PubMed1982

The regulatory region of the divergent argECBH operon in Escherichia coli K-12.

The nucleotide sequence of the control region of the divergent argECBH operon has been established in the wild type and in mutants affecting expression of these genes. The argE and argCBH promoters face each other and overlap with an operator region containing two domains which may act as distinct repressor binding sites. A long leader sequence - not involved in attenuation - precedes argCBH. Overlapping of the argCBH promoter and the region involved in ribosome mobilization for argE translation explains the dual effect of some mutations. Mutations causing semi-constitutive expression of argE improve putative promoter sequences within argC. Implications of these results regarding control mechanisms in amino acid biosynthesis and their evolution are discussed.

Base Sequence↗
PubMed1982

IS3 can function as a mobile promoter in E. coli.

We had shown previously (3) that the E. coli argE gene could be turned-on by an IS3 element inserted in orientation II near the 5' end of the gene. Here we show that this effect is due to the presence of an outward promoter located on IS3. The exact site of insertion of IS3 was determined by DNA sequencing. Using the S1 nuclease mapping technique with in vivo transcribed RNA we located the promoter responsible for argE transcription on IS3 itself outside the region involved in the inverted repeats of this element. IS3 may therefore be considered as a mobile promoter.

Base Sequence↗
PubMed1982

Homologous control sites and DNA transcription starts in the related argF and argI genes of Escherichia coli K12.

The argF and argI genes code for similar proteins able to assemble into hybrid isoenzymes and are therefore thought to share a common origin. We show here that the nucleotide sequence of the promoter and operator regions of these two genes are highly homologous. DNA regions preceding the control sites also present significant homologies. The results support the notion of divergent evolution of the two genes from a common ancestor. Like argE and argCBH , argF and argI are controlled by a repressor molecule recognizing a family of similar operator sites. Attenuation appears to play no role in this regulation.

Base Sequence↗
PubMed1982

Promoter mapping and selection of operator mutants by using insertion of bacteriophage Mu in the argECBH divergent operon of Escherichia coli K-12.

The analysis of a large number of Arg mutants obtained by inserting phage Mu in the argECBH cluster of genes confirmed the "facing" arrangement proposed earlier for the promoters of argE (argEp) and argCBH (argCBHp) and clarified remaining ambiguities regarding the localization of argEp. Casadaban and Cohen's Mu d lac phages (M. Casadaban and S. N. Cohen, Proc. Natl. Acad. Sci. U.S.A. 76:4530-4533, 1979) were used to construct strains where either an intact or a truncated lacZ gene was fused to argC or argB. Several operator-constitutive mutations could be selected for in such strains; the mutations affected both arms of the cluster, thereby defining one common operator region for both directions of transcription.

Bacteriophage lambda↗
PubMed1980

Deletions and DNA rearrangements within the transposable DNA element IS2. A model for the creation of palindromic DNA by DNA repair synthesis.

Three derivatives of mutant ga10P-308::IS2-I of Escherichia coli were characterized by DNA sequence analysis. Deletions and DNA sequence rearrangements were observed which apparently were initiated at short A-T rich inverted repeats within IS2. Two of the mutants carried newly synthesized DNA sequences which were inverted copies of already existing IS2 sequences. Thus long stretches with twofold symmetry were formed. It is discussed whether these inverted repeats were formed by DNA repair synthesis which was initiated at the A-T rich palindromes of IS2.

Base Sequence↗
PubMed1980

The structure of unstable constitutive revertants of mutant galOP-308::IS2-I.

The isolation and characterization of three unstable and constitutive revertants of mutant galOP-308 of E. coli is described. In this mutant an IS2 element is integrated between the promoter and the first structural gene of the galactose operon, and exerts a strong polar effect on the expression of the three galactose genes. In the three revertants under investigation it was observed that relief of polarity and constitutive expression of the gal-operon were accompanied by the deletion of 90% of the IS2 sequence and of various lengths of the adjacent sequences including the gal-promoter. We conclude from this result that the transcription termination signals causing strong polarity were located on the deleted part of IS2, and that in our revertants the galactose genes are now under the control of a new promoter which is apparently unstable.

Chromosome Deletion↗
PubMed1980

Patterns of polarity in the Escherichia coli car AB gene cluster.

The direction of transcription of the carAB gene cluster, which codes for Escherichia coli carbamoylphosphate synthase, was deduced from the effects of phage Mu-1 insertions in each of the two genes and from the results of ribonucleic acid-deoxyribonucleic acid hybridization experiments relating the quantity of car messenger ribonucleic acid to the location of various car mutations. The car locus appears to constitute an operon polarized from carA to carB. The levels of carA and carB products were determined in a large number of car mutants by using in vitro and in vivo complementation assays. The results obtained display strong anomalies, which are discussed in light of the conclusions described above.

Bacteriophage mu↗
PubMed1979

Tandem and inverted repeats of arginine genes in Escherichia coli: structural and evolutionary considerations.

Duplications of arg genes produced in the Rec+ and in the recA genetic backgrounds are shown by heteroduplex analysis to be strictly tandem at the level of resolution of this technique. The formation of these particular rearrangements therefore does not require the inclusion of transposons or other sequences of an appreciable size in their final structure. Duplications of short segments (about 2,000 nucleotides) appear unexpectedly stable when compared with duplications of longer segments (about 10,000 nucleotides). One of the structures analyzed displays two inversely repeated argE genes rearranged into an artificial divergent operon. The bearing of this observation on the origin of bipolar operons, of "mirror-image" map symmetries and on the production of inverted repeats in general, is discussed.

Arginine↗
PubMed1979

Cloning and endonuclease restriction analysis of argF and of the control region of the argECBH bipolar operon in Escherichia coli.

A 1.8 kb DNA fragment, liberated by endonuclease HindIII, contains the control region of the argECBH bipolar operon near one end and the weak secondary promoter of argH at the other extremity; it has been cloned in plasmid pBR322. The same plasmid vector has been used to clone the argF gene liberated from the chromosome by endonuclease BamHI. Restriction patterns for the two hybrid plasmids have been determined, using enzymes AluI, BglI, EcoRI, HaeIII, HincII, HindIII, HpaI and II, PstI and SalI. Two AluI sites situated on either side of and close to a HincII target delineate two short fragments covering the whole of the argECBH control region. The argF control elements are located in a region accessible to further dissection by BamHI, EcoRI, PstI and HindIII. Carriers of the argF plasmid produce extremely high amounts of ornithine carbamoyltransferase, a feature useful for purification of this enzyme.

Arginine↗
PubMed1978

Studies on the control region of the bipolar argECBH operon of Escherichia coli. I. Effect of regulatory mutations and IS2 insertions.

Several mutations affecting the control or the potential of gene expression in the argECBH bipolar operon have been characterized by enzyme assays, genetic mapping, dominance tests and pulse labelled RNA determinations. None of the mutations involves DNA rearrangements detectable by heteroduplex analysis (Charlier et al., 1978). Partially constitutive transcription of both argE and argCBH has been observed in mutant L10 while constitutive argE transcription and normal argCBH control characterize mutants L9, LL13 and LL2. The control region thus appears to contain two overlapping operators, as suggested previously (Elseviers et al., 1972). Two mutants (L2, LL1) and strain 6-8 from Bretscher and Baumberg (1976) display an increase in acetylornithinase specific activity (argE product) without concommittant increased argE transcription. In addition, they exhibit a decreased argCBH transcription. It is suggested that in these organisms, argE translation and argCBH transcription may be affected by the same genetic event; this explanation is compatible with present working hypothesis for the structure of the control region. An interpretation in terms of messenger attenuation also appears possible. From the properties of two strains harbouring an IS2 insertion in the control region (Charlier et al., 1978) the following conclusion may be drawn: 1. When inserted in orientation I close to the proximal end of a silent gene IS2 appears to promote a low but detectable transcription readthrough into that gene. 2. Insertion of an IS2 element in orientation II close to a neighbouring gene is not a sufficient condition to express that gene at a high rate. The properties of the two insertions appear compatible with the structure proposed for the control region.

Acetyltransferases↗