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M Lemonnier

Publications and source records attributed to M Lemonnier.

At least 19 recordsLinked to original sources
PubMed2004

The in vivo form of the murine class VI POU protein Emb is larger than that encoded by previously described transcripts.

The class VI POU domain family member known as Emb in the mouse (rat Brn5 or human mPOU/TCFbeta1) is present in vivo as a protein migrating at about 80 kDa on western blots, considerably larger than that predicted (about 42 kDa) from previously cloned coding sequences. By RT-PCR and 5' RACE strategies a full-length Emb sequence, Emb FL, is now identified. Shorter sequences encoding the -COOH terminal, and an -NH(2) terminal isoform, EmbN, were also isolated. Comparisons of Emb coding sequences between species, including the full-length zebra fish, POU(c), are presented, together with a compilation of the multiple transcripts produced by alternative splicing and the presence of different transcriptional start and stop sites, from the Emb gene.

Alternative Splicing↗
PubMed2004

A novel complex regulates cardiac actin gene expression through interaction of Emb, a class VI POU domain protein, MEF2D, and the histone transacetylase p300.

Expression of the mouse cardiac actin gene depends on a distal enhancer (-7 kbp) which has been shown, in transgenic mice, to direct expression to embryonic skeletal muscle. The presence of this distal sequence is also associated with reproducible expression of cardiac actin transgenes. In differentiated skeletal muscle cells, activity of the enhancer is driven by an E box, binding MyoD family members, and by a 3' AT-rich sequence which is in the location of a DNase I-hypersensitive site. This sequence does not bind MEF2 proteins, or other known muscle transcription factors, directly. Oct1 and Emb, a class VI POU domain protein, bind to consensus sites on the DNA, and it is the binding of Emb which is important for activity. Emb binds as a major complex with MEF2D and the histone transacetylase p300. The form of Emb present in this complex and as a major form in muscle cell extracts is longer (80 kDa) than that previously described. These results demonstrate the importance of this novel complex in the transcriptional regulation of the cardiac actin gene and suggest a potential role in chromatin remodeling associated with muscle gene activation.

Acetyltransferases↗
PubMed2000

Disruption of the F plasmid partition complex in vivo by partition protein SopA.

The SopA protein plays an essential, though so far undefined, role in partition of the mini-F plasmid but, when overproduced, it causes loss of mini-F from growing cells. Our investigation of this phenomenon has revealed that excess SopA protein reduces the linking number of mini-F. It appears to do so by disturbing the partition complex, in which SopB normally introduces local positive supercoiling upon binding to the sopC centromere, as it occurs only in plasmids carrying sopC and in the presence of SopB protein. SopA-induced reduction in linking number is not associated with altered sop promoter activity or levels of SopB protein and occurs in the absence of changes in overall supercoil density. SopA protein mutated in the ATPase nucleotide-binding site (K120Q) or lacking the presumed SopB interaction domain does not induce the reduction in linking number, suggesting that excess SopA disrupts the partition complex by interacting with SopB to remove positive supercoils in an ATP-dependent manner. Destabilization of mini-F also depends on sopC and SopB, but the K120Q mutant retains some capacity for destabilizing mini-F. SopA-induced destabilization thus appears to be complex and may involve more than one SopA activity. The results are interpreted in terms of a regulatory role for SopA in the oligomerization of SopB dimers bound to the centromere.

Bacterial Proteins↗
PubMed1997

Genetic basis of the MbrC "ploidy" phenotype in Escherichia coli.

The mbrC17 mutation in Escherichia coli had been shown to cause conditional growth defects and an increase in the quantity of DNA per cell. The present work was aimed at identifying the mutation. Sequencing showed that the MbrC17 phenotype does not involve glr (murI), as previously suggested. P1 transduction data indicated that the mbrC17 mutation is closely linked to rpoB, and allele exchange showed it to lie within the secE-nusG operon. A single change relative to wild type was found in the secE-nusG region from the mbrC17 strain, a G-->A mutation 23 bp upstream of the secE coding sequence. This mutation causes a two-fold increase in the concentration of secE-nusG mRNA.

Amino Acid Isomerases↗
PubMed1996

Bronchial responsiveness and inflammation in guinea-pigs exposed to toluene diisocyanate: a study on single and repeated exposure.

The question of whether or not toluene diisocyanate (TDI)-induced airway hyperresponsiveness in the guinea-pig is accompanied by neutrophil influx into bronchoalveolar lavage fluid (BALF) was addressed. Two modes of exposure were studied; (1) acute exposures where animals were exposed to 3 ppm TDI for 1 h and experiments were carried out 30 min, 4 h, 24 h, 48 h and 1 week after the TDI exposures; (2) subacute exposures where animals were exposed to 0.080 and 0.046 ppm TDI for 48 h 1 week, respectively, and experiments were carried out 24 h after the TDI exposures. The changes in airway responsiveness to increasing doses of intravenous acetylcholine (ACh) in anaesthetized and tracheotomized spontaneously breathing guinea-pigs were examined. In order to elucidate the possible relationships of airway responsiveness to cellular infiltration, bronchoalveolar lavage was performed in additional group of guinea-pigs exposed to the same conditions. After acute exposure to 3 ppm TDI, increased bronchial responsiveness was evident within 30 min, lasted 48 h, but had vanished 1 week after the exposure. An influx of neutrophils occurred into the BALF within 1 h after exposure. The influx of neutrophil into BALF lasted 48 h and vanished 1 week after the end of exposure. After 48 h of exposure to TDI at 0.080 ppm, or 0.046 ppm for 1 week, increased bronchial responsiveness was evident 24 h after the end of the both modes of exposure, but no influx of neutrophils was observed into the BALF. It was concluded that even though the neutrophil influx and hyperresponsiveness evolve in the same way after acute exposure to a high concentration of TDI (3 ppm), this is not the case after subchronic exposure to low concentrations of TDI, where a bronchial hyperresponsiveness is observed without detectable neutrophil influx.

Acetylcholine↗
PubMed1994

Promoter elements and transcriptional control of the chicken tropomyosin gene [corrected].

The chicken beta tropomyosin (beta TM) gene has two alternative transcription start sites (sk and nmCAP sites) which are used in muscle or non muscle tissues respectively. In order to understand the mechanisms involved in the tissue-specific and developmentally-regulated expression of the beta TM gene, we have analyzed the 5' regions associated with each CAP site. Truncated regions 5' to the nmCAP site were inserted upstream to the bacterial chloramphenicol acetyltransferase (CAT) reporter gene and these constructs were transfected into avian myogenic and non myogenic cells. The maximum transcription is driven by the CAT construct (-168/ + 216 nt) in all cell types. Previous deletion analysis of the region 5' to the beta TMskCAP site has indicated that 805 nt confer myotube-specific transcription. In this work, we characterized an enhancer element (-201/-68 nt) which contains an E box (-177), a variant CArG box (-104) and a stretch of 7Cs (-147). Mutation of any of these motifs results in a decrease of the myotube-specific transcriptional activity. Electrophoretic mobility shift assays indicate that these cis-acting sequences specifically bind nuclear proteins. This enhancer functions in an orientation-dependent manner.

Animals↗
PubMed1993

Denervated chicken breast muscle displays discoordinate regulation and differential patterns of expression of alpha f and beta tropomyosin genes.

The expression of the alpha fast (alpha f) and beta tropomyosin (TM) genes has been analysed with muscle-specific and common cDNA probes after unilateral nerve section of the pectoralis major muscle (PM) in 4-week-old chickens. The following were observed in denervated muscles. (1) The beta TM mRNA, which was repressed during development, reaccumulates in a biphasic curve with the increase in the beta TM protein lagging behind the changes in its mRNA. Accordingly, no beta TM is seen in products translated in vitro from total and polyA+ RNA obtained 1 week after denervation. No such translation block is seen with RNA obtained from control or muscles denervated for 6 weeks. (2) No changes in the alpha fTM mRNA and corresponding protein are observed. (3) RNA processing of the two genes is not changed. (4) In the contralateral muscles, transitory increases in alpha f and beta TM mRNAs are observed while the corresponding proteins remain unchanged. Our data suggest that muscle fibres display early and long-term responses to the loss of neural input which might result from a combination of changes produced by regenerative processes and reprogramming of existing fibres. Moreover, in contrast to normal development, no reciprocal changes of alpha f and beta TM expression are seen in denervated muscles.

Animals↗
PubMed1993

The muscle specific promoter of chick beta tropomyosin gene requires helix-loop-helix myogenic regulatory factors and ubiquitous transcription factors.

The chick beta tropomyosin (TM) gene has two alternative transcription initiation start sites which are used in muscle or non muscle tissue. A recombinant plasmid containing 805 nucleotides (nt) of the sequence upstream to the muscle CAP site driving the bacterial chloramphenicol acetyltransferase gene is sufficient for muscle specific expression. Of the two E boxes present in this construct, only the E box proximal to the CAP site is functional since deletion or mutation of this E box causes a decrease of CAT activity (about 40%). Separate mutation of Sp1 motifs also reduces the transcription driven by the 805nt fragment. Double mutation of E box and Sp1 motifs show that helix-loop-helix muscle regulatory factors and ubiquitous Sp1 transcription factor are required in the initiation of the transcription of the chick beta TM gene in muscle tissue. Our results also suggest that other factors may participate to this process.

Animals↗
PubMed1991

The chicken gene encoding the alpha isoform of tropomyosin of fast-twitch muscle fibers: organization, expression and identification of the major proteins synthesized.

The chicken gene alpha fTM encoding the alpha-tropomyosin of fast-twitch muscle fibers (alpha fTM) covers 20 kb and consists of 15 exons. From this gene, three types of mature transcripts (1.3 kb, 2 kb and 2.8 kb) are expressed through the use of alternative promoters, alternatively spliced exons and multiple 3' end processing. Northern analysis and S1 mapping have shown that the 1.3-kb transcript (exons 1a, 2b, 3, 4, 5, 6b, 7, 8, 9a-9b) is expressed in fast-twitch skeletal muscles and that 2-kb transcripts are expressed in smooth muscle (exons 1a, 2a, 3, 4, 5, 6b, 7, 8, 9d) and in fibroblasts (exons 1a, 2b, 3, 4, 5, 6a or 6b, 7, 8, 9d). These 2-kb transcripts encode distinct proteins which we have identified by two-dimensional (2D) gel electrophoresis. The 2.8-kb transcript which has not been so far characterized in birds is expressed in brain (exons 1b, 3, 4, 5, 6b, 7, 8, 9c-9d). This transcript has been characterized by a cDNA polymerase chain reaction assay and by S1 nuclease mapping. It produces a major TM isoform of chick brain which we have identified by 2D gels.

Amino Acid Sequence↗
PubMed1991

Interdependence of polymorphonuclear neutrophils and macrophages stained for N-acetyl-beta-glucosaminidase in lavage effluents from toluene diisocyanate-exposed rat lungs.

Male Sprague-Dawley rats were exposed to toluene diisocyanate (TDI) concentrations between 0.082 and 1.087 ppm for 4 h, and pulmonary lavage was carried out 24 h after initiation of the exposure. Cells recovered from the lavage effluents of TDI-exposed rat lungs were identified and counted, then pulmonary macrophages (PMs) resulting from cytocentrifuged preparations were examined for N-acetyl-beta-glucosaminidase (NAG) cytochemical staining. Exposure to TDI led to a parallel and concentration-dependent increase in the number of polymorphonuclear neutrophils (PMNs) and the proportion of PMs stained for NAG, suggesting that the same primary event initiates the two cell responses.

Acetylglucosaminidase↗
PubMed1990

A nonmuscle tropomyosin is encoded by the smooth/skeletal beta-tropomyosin gene and its RNA is transcribed from an internal promoter.

The smooth/skeletal muscle beta-tropomyosin gene contains an additional exon (exon 1') which is located between exons 2 and 3 and which is used to generate a 1.3-kb transcript expressed in undifferentiated muscle as well as nonmuscle cells. This mRNA, besides exon 1', corresponds to exons 3, 4, 5, 6A, 7, 8, and 9B of the gene and codes for a 247-amino acid low molecular weight tropomyosin. Exon 1' contains the coding sequence for the first 44 amino acids of the protein as well as the whole 5'-untranslated region. During the transition from myoblasts to myotubes, initiation of transcription continues from the internal promoter but also occurs from the distal promoter in order to give rise to the skeletal beta-tropomyosin-specific transcript.

Amino Acid Sequence↗
PubMed1989

A single gene codes for the beta subunits of smooth and skeletal muscle tropomyosin in the chicken.

A chicken genomic DNA library was screened with a full length cDNA corresponding to the beta subunit of smooth muscle tropomyosin. When hybridized with RNAs isolated from various tissues, this cDNA recognizes two mRNA species: one of 1.3 kilobase pairs present only in smooth muscle and one of 1.6 kilobase pairs present only in skeletal muscle. Two overlapping recombinant phages were shown to contain the entire locus and were further characterized. This locus contains 11 exons and spans approximately 13 kilobase pairs. Exon 1 (amino acids 1-38) contains the 5'-untranslated region which is common to the two mRNAs. Exons 6 (amino acids 189-213) and 11 (amino acids 258-284) contain sequences which are present exclusively in the 1.3-kilobase pair smooth muscle mRNA while exons 7 and 10, which code for an analogous region, contain sequences which are present exclusively in the 1.6-kilobase pair skeletal muscle mRNA (exons 10 and 11 also contain the entire 3'-untranslated regions of the corresponding mRNAs). Other exons, 2 to 5 (amino acids 39-188) and 8 and 9 (amino acids 214-257), contain sequences which are present in both mRNAs. Our results indicate that both the smooth and skeletal beta-tropomyosin mRNAs are derived from transcripts of a single gene with a unique promoter by a differential splicing mechanism.

Amino Acid Sequence↗
PubMed1989

Multiple mRNAs encode peripherin, a neuronal intermediate filament protein.

Three cDNA clones of 1.6 (3u), 1.2 (5g) and 0.6 (5b) kbp, specific for peripherin, a neuronal intermediate filament protein (IFP), have been isolated from a murine neuroblastoma cell lambda gt11 library by immunoscreening using peripherin antiserum. Antibodies eluted from the fusion proteins produced by clones 3u and 5g recognize the peripherin spots on immunoblots. Where they overlap the three cDNAs have identical sequences. cDNA 5g exhibits the closest homology to type III IFP cDNAs. cDNA 3u is identical to the corresponding region of cDNA 5g, except for the insertion of a 96 bp fragment at a position corresponding to the junction of exons 4 and 5 in type III IFP cDNAs. cDNA 5b is also identical to the corresponding region of cDNA 5g, except for the deletion of a 62 bp fragment at the junction of exons 8 and 9 in type III IFP cDNAs. S1 mapping experiments performed with probes covering the 3' end of the two unexpected regions show that three distinct mRNAs correspond to the three cDNAs. Moreover, three peripherin products, two minor 61 and 56 kd products in addition to the major 58 kd peripherin, are observed when poly(A)+ RNA is in vitro translated, the 61 kd peripherin being translated from the 3u-selected RNA. The three RNAs originate from alternative splicing of a unique peripherin gene, thus generating polymorphism of peripherin.

Amino Acid Sequence↗
PubMed1989

Tissue-specific transcriptional control of alpha- and beta-tropomyosins in chicken muscle development.

During muscle maturation, isoform switching of contractile proteins to attain the adult phenotype involves both stage-specific and muscle-specific regulatory mechanisms. Chicken pectoralis major (PM) provides an interesting model to study the latter since a specific pattern of tropomyosin (TM) with repression of the beta TM isoform is displayed by the adult PM. The developmental pattern of alpha and beta fast skeletal muscle tropomyosins' (alpha f and beta TM) RNAs was investigated with 3' untranslated region specific probes. In PM, the beta TM messenger ceased to accumulate after hatching through a transcriptional control, as shown by run-on assays, so that, at Day 8 ex ovo, no beta TM mRNA was detected. In this same muscle, in parallel with the disappearance of the beta TM mRNA, there was a boost in the accumulation of the alpha f TM mRNA. In the leg muscles, following hatching, there was only a moderate increase in the level of the alpha f TM mRNA, together with a slight decrease in the accumulation of the beta TM mRNA. Taken together, these results show that chicken muscle maturation involves tissue-specific transcriptional control of tropomyosin genes and could suggest a possible coordinate regulation of the two genes.

Animals↗
PubMed1988

[Regulation of the expression of alpha and beta tropomyosin genes during development of the pectoral muscle in the chicken].

Accumulation of mRNAs coding for alpha and beta skeletal tropomyosins was investigated using specific probes and normalized to muscle creatine kinase (M-CK) mRNA by slot-blot assays. In developing pectoralis muscle, the ratio of alpha TM messenger/M-CK remained constant until hatching, at which time the messenger disappeared within a week. However, in the leg, this ratio remained constant until 8 days after hatching, whereafter it decreased progressively to reach 30% in the adult. The alpha TM/M-CK ratios were almost the same in the embryonic leg and pectoralis muscle. After hatching, there was a large increase in pectoralis muscle (x 3 at day +4, x 0 at day +21) whereas, the increase was less pronounced and more progressive in the leg (x 3 at day 21). Run-on assays showed that nuclei isolated from 15-day in ovo leg and pectoralis muscles had similar patterns of muscle specific gene transcription whereas post-hatched pectoralis muscle nuclei were shown to have a higher rate of alpha to beta tropomyosin gene transcription. These data are in accordance with the results obtained for protein analysis of leg and pectoralis muscles and support the notion that changes in the protein pattern of developing muscle can be relevant to coordinate regulation of gene transcription.

Animals↗