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Biomedical subjects

B Robert

Publications and source records attributed to B Robert.

At least 145 records · Page 8Linked to original sources
PubMed1988

Promoter analysis of myosin alkali light chain genes expressed in mouse striated muscle.

There are three principal myosin alkali light chain (MLC) genes expressed in mouse striated muscle. The skeletal muscle gene MLC1F/MLC3F, the ventricular muscle/slow skeletal muscle gene MLC1V(MLC1S), and the atrial muscle/foetal striated muscle gene MLC1A(MLC1emb). MLC1V and MLC1A are expressed in both cardiac and skeletal muscle, and we show here that these genes use a single site of initiation of transcription, and therefore the same proximal promoter region, in both muscle types, and in myogenic cell lines in culture. We have previously shown that for the MLC1F/MLC3F gene, 1200bp of upstream sequence from the MLC1F promoter is sufficient to allow tissue specific and developmentally regulated expression. We have therefore isolated, characterised, and sequenced over 1200bp upstream of each of the three MLC genes in order to look for elements which may be involved in their regulation. Detailed comparison of their promoter sequences, as well as those of the cardiac and skeletal muscle alpha-actin genes, reveals a number of common elements. Among these is an "MLC-sequence" (CCTTTTATAG) common to all MLC genes, including those of chick and rat, and a "cardiac sequence" common to the mouse MLC1A, MLC1V and alpha-cardiac actin genes expressed in the heart.

Amino Acid Sequence↗
PubMed1988

Structure and sequence of the myosin alkali light chain gene expressed in adult cardiac atria and fetal striated muscle.

Mammalian cardiac muscle contains two myosin alkali light chains which are the major isoforms present in either atrial (MLC1A) or ventricular (MLC1V) muscle, and which are different from the fast skeletal muscle isoforms (MLC1F and MLC3F). The atrial isoform is also expressed in fetal skeletal and fetal ventricular muscle, where this isoform is also described as the fetal isoform MLC1emb. We have previously isolated a cDNA clone encoding part of the mouse MLC1A/MLC1emb isoform and have used this clone to demonstrate the identity of MLC1A and MLC1emb in the mouse. To date no information on the amino acid sequence of this mammalian atrial/fetal isoform has been available. Here we present the complete structure and sequence of the mouse MLC1A/MLC1emb gene, together with the predicted amino acid sequence of this isoform. Comparison of the MLC1A/MLC1emb gene and polypeptide with those of MLC1F and MLC1V suggests that MLC1A/MLC1emb and MLC1V were generated from a common ancestral gene. The NH2-terminal region of MLC1A/MLC1emb, thought to be involved in the actomyosin interaction, shows conservation with MLC1V but not with MLC1F suggesting a shared functional domain in these cardiac isoforms. Comparison with the chicken embryonic MLC (L23) suggests that although MLC1A/MLC1emb and L23 show very different patterns of expression, both during development and in the adult, they probably represent the homologous gene in these two species.

Amino Acid Sequence↗
PubMed1988

Assignment of the human fast skeletal muscle myosin alkali light chains gene (MLC1F/MLC3F) to 2q 32.1-2qter.

A DNA probe derived from a mouse intronless pseudogene including coding regions for the myosin fast skeletal muscle alkali light chains, MLC1F/MLC3F (suggested HGM symbol, MYL1), was tested on a panel of 25 independent man-rodent somatic cell hybrids in order to assign the human MLC1F/MLC3F gene to a human chromosome. A 3.7-kb TaqI human fragment was found to correlate with the presence of chromosome 2 in the hybrids, characterized both by cytogenetic analysis and reference enzyme markers. A regional assignment to 2q32.1-qter was possible using hybrids whose human parental strains bore a reciprocal translocation t(X;2) (p22;q32.1). The fact that IDH1 and the MLC1F/MLC3F gene are closely linked on chromosome 1 in the mouse and map to the same region of human chromosome 2 in man indicates, that these chromosomes have a conserved region of homology between them and that the human 3.7-kb TaqI fragment corresponds indeed to a functional gene.

Animals↗
PubMed1986

Chromosomal localization of muscle nicotinic acetylcholine receptor genes in the mouse.

The chromosomal localization of the genes encoding the four subunits of muscle nicotinic receptor was determined by analyzing restriction fragment length polymorphisms between two mouse species Mus musculus domesticus (DBA/2) and Mus spretus (SPE). Analysis of the progeny of the interspecies mouse backcross (DBA/2 X SPE) X DBA/2 showed that the alpha-subunit gene cosegregates with the alpha-cardiac actin gene on chromosome 17, that the beta-subunit gene is located on chromosome 11, and that the gamma- and delta-subunit genes cosegregate and are located on chromosome 1.

Actins↗
PubMed1986

Actin and myosin multigene families: their expression during the formation and maturation of striated muscle.

The initial formation of skeletal muscle fibers is accompanied by the expression of muscle-type actin and myosin genes. During subsequent maturation of muscle fibers in vivo, developmental changes in the fetal/adult isoforms of these proteins occur. Skeletal muscle-specific transcripts coding for different myosin heavy chains accumulate sequentially both in vivo and in vitro. A genetic analysis demonstrates that these genes are clustered, implicating cis-acting regulatory factors. In contrast, actin and myosin light chain genes are dispersed in the mouse genome. These gene families show a different developmental "strategy": Genes expressed in adult cardiac tissue are coexpressed with the corresponding skeletal muscle sequence during fetal development. This phenomenon also occurs in adult tissue. Under conditions of cardiac overload, adult rat hearts accumulate skeletal actin mRNA and cardiac actin transcripts. In some mouse lines, a mutant cardiac actin gene locus is present. The presence of a second active upstream promoter at this locus depresses transcription of the bone fide gene, resulting in low levels of mature cardiac actin mRNA. In this situation skeletal actin gene transcripts accumulate. Genes expressed in the same fetal or adult muscle phenotype are not linked, suggesting that their coexpression is regulated by transacting factors. The promoter regions of such genes in the mouse have no common characteristics of primary structure with the exception of an E1A-type enhancer core sequence, which has a conserved 5' flanking element, seen for actin and myosin light chain genes. Reintroduction of these promoter regions into muscle cells provides a functional test for such potential regulatory sequences.

Actins↗
PubMed1985

The myosin alkali light chains of mouse ventricular and slow skeletal muscle are indistinguishable and are encoded by the same gene.

We have isolated a cDNA recombinant plasmid (pA29) identified as encoding part of the ventricular muscle myosin light chain MLC1v. This cDNA contains a 300-base pair fragment which under conditions of moderate stringency shows specific hybridization to MLC1v mRNA with no detectable cross-hybridization with the mRNAs encoding the fast skeletal muscle isoforms MLC1F and MLC3F, or the atrial muscle isoform MLC1A. Under these conditions hybridization is seen with an abundant mRNA present in slow skeletal muscle (soleus) which is indistinguishable from ventricular MLC1V mRNA on the basis of size and of thermal stability of hybrids formed with plasmid pA29. The mouse MLC1V and MLC1S proteins are found to co-migrate on two-dimensional gels. We therefore conclude that these isoforms are the same and are encoded by the same mRNA. Analysis of mouse DNA has identified a single region of the genome which hybridizes to this same fragment of pA29. This region has been isolated in a recombinant phage and has been shown to contain a single gene showing homology with MLC1V mRNA by R-loop analysis. We therefore conclude that MLC1V and MLC1S are encoded by a single gene. The pattern of segregation of a restriction fragment length polymorphism identified for this gene between Mus musculus and Mus spretus has been followed in an F1 backcross between these two mouse species. The results show the MLC1V/MLC1S gene to be closely linked to a marker at the distal end of mouse chromosome 9.

Animals↗
PubMed1985

A comparison between mammalian and avian fast skeletal muscle alkali myosin light chain genes: regulatory implications.

A single locus in the mouse, rat and chicken encodes both alkali myosin light chains, MLC1F and MLC3F. This gene has two distinct promoters and gives rise to two different primary transcripts, which are processed by alternative and different modes of splicing to form MLC1F and MLC3F mRNAs. The MLC1F/MLC3F gene is very similar between mouse, rat and chicken, in terms of its overall structure, the length and location of the introns, and the splice site consensus sequences. Nucleotide sequences of coding regions are very conserved but 3' and 5' non coding regions of the mRNAs have diverged. In the MLC1F promoter regions, several blocks of nucleotides are highly conserved (more than 70% homology), especially a sequence of about 70 nucleotides, located between positions -80 and -150 relative to the Cap site. Conserved blocks of homology are also found in the MLC3F promoter regions, although the common sequences are shorter. The presence of such highly conserved nucleotide sequences in the 5' flanking regions suggests that these sequences are functionally important in initiation of transcription and regulation of expression of this complex gene. Primer extension experiments indicate multiple cap sites for MLC3F mRNA.

Amino Acid Sequence↗
PubMed1985

The same myosin alkali light chain gene is expressed in adult cardiac atria and in fetal skeletal muscle.

We have isolated from a cDNA library constructed using mouse cardiac mRNA sequences, a clone (pC6) homologous to part of the mRNA encoding the myosin alkali light chain MLC1A from adult mouse atria. This sequence also hybridizes to mRNA encoding the fetal light chain form MLC1emb expressed in both fused myotubes in culture and in 18 day fetal skeletal muscle. These mRNA sequences are indistinguishable from the MLC1A messenger both on the basis of size and of their thermal stability of hybridization. In vitro translation of mRNA selected by hybridization with pC6 results in a protein that comigrates with the fetal MLC1emb isoform, and two-dimensional gel electrophoresis of adult atrial and fetal skeletal muscle proteins shows MLC1A and MLC1emb to be indistinguishable in the mouse. Southern blot hybridization of clone pC6 to mouse genomic DNA and the analysis of restriction fragment length polymorphisms between different mouse species demonstrates the presence of a single hybridizing locus in the mouse genome. These data provide strong evidence that the atrial MLC1A and fetal skeletal MLC1emb isoform are encoded by the same gene and by the same mRNA and are thus identical proteins.

Animals↗
PubMed1985

Chromosomal distribution of genes coding for fast twitch skeletal muscle myosin light chains.

The mouse fast twitch skeletal muscle myosin light chains are encoded by a multigene family which comprises the gene coding for the myosin light chain 2 (Myl2f), and the gene coding for both myosin light chains 1 and 3 (Myl1f/Myl3f). In addition, a Myl1f/Myl3f-related pseudogene is present in the domestic mouse Mus musculus. The members of this gene family were assigned to chromosomes by molecular hybridization, using DNA extracted from a panel of cloned mouse-Chinese hamster somatic hybrid cells and specific DNA probes. The genes coding for the light chains of the myosin molecule are dispersed on several chromosomes, while genes coding for the heavy chain of myosin are located on a single, different chromosome.

Animals↗
PubMed1985

Structural characterization of high 800 nm-absorbing light-harvesting complexes from Rhodospirillales from their resonance Raman spectra.

Resonance Raman spectroscopy provided evidence that high 800 nm-absorbing antennae from Rhodopseudomonas (Rps.) acidophila and Rps. palustris have similar structures around their dweller bacteriochlorophylls. These host-site structures are different from those of B 850-800 complexes from Chromatiaceae, which also exhibit a high absorbance at 800 nm. As also shown by previous biochemical data, these complexes might be stoichiometrically different from other antenna complexes, having one more BChl per minimal size unit of protein. A new classification of B 850-800 complexes is proposed, on the basis of resonance Raman and biochemical data: this classification distinguishes a class of B 850-800 S (involving the B 850-800 complexes from sulfur purple bacteria), two classes of B 850-800 NS (involving the B 850-800 complexes from non sulfur purple bacteria) and a class of H 800 complexes (involving the B 850-800 complexes from non sulfur purple bacteria exhibiting a high absorbance at 800 nm).

Bacterial Proteins↗
PubMed1984

A single locus in the mouse encodes both myosin light chains 1 and 3, a second locus corresponds to a related pseudogene.

Two loci have been characterized in the mouse Mus musculus, which are homologous to the mRNAs encoding myosin light chains MLC1F and MLC3F, two proteins with a common -COOH terminal sequence. One of these loci is an intronless pseudogene, absent from the mouse species Mus spretus; alterations in its nucleotide sequence preclude it from generating a functional MLC1F or MLC3F. The other contains the genetic information for the two proteins. The part common to both proteins is encoded by five exons, which cover about 6.5 kb. Genetic information specific for the N-terminal sequences is encoded in four exons, at 3.5 and 14.3 kb for MLC1F, and 3.8 and 4.5 kb for MLC3F, upstream of the first common exon. Each 5' terminus has a TATA-like consensus sequence about 30 bases upstream of the cap site. The pseudogene is not genetically linked to the functional MLC1F/MLC3F locus in the genome of Mus musculus.

Amino Acid Sequence↗
PubMed1983

Sequential accumulation of mRNAs encoding different myosin heavy chain isoforms during skeletal muscle development in vivo detected with a recombinant plasmid identified as coding for an adult fast myosin heavy chain from mouse skeletal muscle.

In order to study developmental transitions of myosin heavy chain gene expression, we have cloned from newborn mouse skeletal muscle a recombinant plasmid (plasmid MHC 32) that contains an insertion coding for the COOH-terminal portion of an adult fast myosin heavy chain isoform of mouse skeletal muscle. By Northern blots and dot blots, it has been shown that the MHC 32 sequence reveals a broad cross-hybridization with RNA from different mammalian striated muscle tissues. Southern blots with mouse genomic DNA show only one homologous gene, but cross-hybridization at lower stringency to seven to eight different bands, some containing multiple genomic fragments, among which are probably the genes encoding the different striated muscle isoforms. S1 protection experiments with RNA from mouse skeletal muscle before and after birth demonstrate that plasmid MHC 32 is homologous to a major mRNA species of adult skeletal muscle. This adult mRNA is a predominant sequence within 5-6 days after birth. It begins to accumulate at 1-3 days; at the 18th day fetal stage, another major mRNA species is detected as partially homologous with the adult MHC 32 sequence. This fetal myosin heavy chain mRNA is still predominant at 1-3 days after birth, but is rapidly (by 5-6 days) replaced by the adult MHC sequence. There is thus a rapid transition after birth from fetal to adult skeletal muscle myosin heavy chain mRNA sequences.

Amino Acid Sequence↗
PubMed1982

cDNA recombinant plasmid complementary to mRNAs for light chains 1 and 3 of mouse skeletal muscle myosin.

A recombinant plasmid with a cDNA sequence transcribed from mouse skeletal muscle RNA is shown to hybridize with mRNAs for myosin light chains LC1F and LC3F. The inserted fragment corresponds exclusively to the 3'-noncoding region of the mRNA. It hybridizes almost exclusively with the two light chain messengers from fast skeletal muscle RNA of adult mouse. Slight hybridization is seen with RNA from heart muscle and embryonic skeletal muscle. The implications of the conservation of the 3'-noncoding regions between the two mRNAs are discussed.

Animals↗