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M Steinmetz

Publications and source records attributed to M Steinmetz.

At least 73 records · Page 4Linked to original sources
PubMed1988

Tolerance in T-cell-receptor transgenic mice involves deletion of nonmature CD4+8+ thymocytes.

The mechanism of self-tolerance is studied in T-cell-receptor transgenic mice expressing a receptor in many of their T cells for the male (H-Y) antigen in the context of class I H-2Db MHC antigens. Autospecific T cells are deleted in male mice. The deletion affects only transgene-expressing cells with a relatively high surface-density of CD8 molecules, including nonmature CD4+ CD8+ thymocytes, and is not caused by anti-idiotype cells.

Animals↗
PubMed1988

A previously undetected MHC gene with an unusual periodic structure.

The major histocompatibility complex is a chromosomal segment embodying several gene clusters among which those with immune functions are the best characterized. This region is suspected to host other as yet undetected genes whose characterization may shed light on the population genetics and evolution of the whole gene complex and thus on its unexplained character of marker locus for a number of diseases of nonimmune or unknown pathogenesis. A novel gene was identified that is transcribed in all tissues tested and is located in mouse and man between the CA and Bf genes of the H-2 and HLA complexes, respectively. From the nucleotide sequence, derived from liver complementary DNA clones, it is predicted that this novel single-copy gene encodes a 42-kilodalton polypeptide that bears no recognizable relation to the protein families known so far, but it displays striking hallmarks of natural selection.

Amino Acid Sequence↗
PubMed1988

In transgenic mice the introduced functional T cell receptor beta gene prevents expression of endogenous beta genes.

Transgenic mice were constructed with a functional T cell receptor beta gene. Transcription of the introduced gene is largely confined to T cells, but low levels of transcripts are also seen in B cells and in other tissues. Serological analyses show that most, if not all, of the T lymphocytes express the transgenic beta chain on the cell surface and lack beta chains encoded by endogenous beta genes. Molecular genetic analyses of uncloned and cloned T lymphocytes demonstrate that rearrangement of endogenous beta genes is incomplete. Partial D beta 1-J beta 1 rearrangements are found preferentially, while complete VDJ rearrangements are not seen. These findings show that expression of the transgene regulates the rearrangement of endogenous beta genes. Although the alpha beta T cell receptors of the transgenic mice are homogeneous with respect to the beta chain, they are fully functional, at least in a variety of allogeneic responses.

Animals↗
PubMed1988

Differential splicing and alternative polyadenylation generates distinct NCAM transcripts and proteins in the mouse.

The neural cell adhesion molecule (NCAM) exists in at least three different protein isoforms which are selectively expressed by different cell types and at different stages of development. They are encoded by four to five different transcripts that are derived from a single gene. Here we report the exon--intron structure of the 3' part of the mouse NCAM gene. This region contains six exons. The 5' exon is constitutively expressed in all four prominent size classes of NCAM mRNAs detected in the mouse brain. The second exon contains the poly(A) addition sites for the two smaller mRNAs of 5.2 and 2.9 kb which differ in the length of their 3' non-coding regions and seem both to encode NCAM-120. This second exon is absent in the largest 7.4 kb transcript which encodes NCAM-180; in the 6.7 kb mRNA, which appears to code for NCAM-140, the second and the fifth exon have been spliced out. This data explains how the prominent four transcripts and three protein isoforms of mouse NCAM are generated from a single gene. The alternatively spliced fifth exon is surrounded by inverted repeats potentially capable of secondary structure formation, that may sequester this exon in a loop.

Amino Acid Sequence↗
PubMed1988

Transcription of T cell receptor beta-chain genes is controlled by a downstream regulatory element.

To characterize cis-acting elements controlling the expression of T cell receptor beta-chains we generated a number of transgenic mouse lines harboring a rearranged T cell receptor beta-chain with different extensions of 5' and 3' flanking sequences. Transcriptional analysis of transgenic mice carrying these clones showed that sequences located downstream of the polyadenylation signal of the C beta 2 region are indispensable for expression in transgenic mice. The sequences conferring enhancer activity in this fragment were further defined by transient CAT assays. Strong enhancer activity was found to reside in a 550 bp fragment located 5 kb downstream from C beta 2. The nucleotide sequence of this fragment revealed a number of oligonucleotide motifs characteristic for enhancer elements.

Animals↗
PubMed1988

The same MHC recombinational hot spots are active in crossing-over between wild/wild and wild/inbred mouse chromosomes.

Four recombinational breakpoints were mapped in the K-A interval of the mouse major histocompatibility complex (MHC) by Southern blot analysis. The breakpoint in B10.SBR, containing a b/s recombinant MHC haplotype, is located about 45 kb upstream of the A beta 2 gene close to the breakpoint in B10.AQR. Crossover in two cas3/cas4 and one cas4/cas3 recombinant haplotypes has taken place in the previously identified K/A beta 3 and A beta 3/A beta 2 recombinational hot spots. The same hot spots are thus active in crossover between two Mus musculus castaneus MHC haplotypes and in crossover between a laboratory and a M. m. castaneus MHC haplotype.

Animals↗
PubMed1987

Analysis of cDNA clones that code for the transmembrane forms of the mouse neural cell adhesion molecule (NCAM) and are generated by alternative RNA splicing.

The neural cell adhesion molecule (NCAM) exists in at least three different isoforms. In the mouse, NCAM proteins with apparent Mr's of 180,000, 140,000 and 120,000 have been distinguished. These are encoded by 4 to 5 different transcripts. Here we report the full amino acid sequence of an isoform which most likely represents NCAM-140. The N-terminal extracellular portion of the 829-residue polypeptide appears to be identical to all three NCAM proteins. The Mr of 91,276 is considerably smaller than the estimate based on SDS-gel electrophoresis. The 147 C-terminal residues are distinct from NCAM-120 and contain the putative transmembrane and cytoplasmic domains. The transcript encoding NCAM-140 contains almost 3.2 kb non-coding sequence with a canonical polyadenylation signal. While the 5' sequences of NCAM-140 hybridize with all NCAM mRNAs, the 3' probes recognize only the two larger transcripts of 7.4 and 6.7 kb. From S1 nuclease protection analyses and hybridization studies of several NCAM cDNA clones with genomic NCAM sequences one can conclude that the different NCAM transcripts are generated by alternative splicing. In addition to the two alternative splice sites in the sequence encoding the extracellular domains, a third one can be predicted approximately 320 nt downstream of the start of the NCAM-140-specific sequence portion. This finding is in agreement with the existence of an extra exon in the chicken NCAM-180. Comparison between mouse and chicken NCAM amino acid sequences revealed the highest homology in the second and fifth Ig-like domains and in the cytoplasmic parts suggesting that these regions serve highly conserved functions.

Amino Acid Sequence↗
PubMed1987

Transcription of a T cell receptor beta chain gene in L cell fibroblasts following DNA-mediated gene transfer.

Functionally rearranged T cell receptor alpha and beta-chain genes from a fluorescein-specific cytotoxic T cell clone have been introduced, together with the selectable marker gene neo, into mouse fibroblasts (L cells) by electroporation. Transformed cells were selected for neo gene expression by growth in medium containing the antibiotic G418. Southern blot analysis of DNA from transformed L cell clones revealed that the endogeneous T cell receptor alpha and beta-chain genes were in germ-line configuration and that in 4 of the 6 clones examined the exogenously introduced rearranged alpha and beta chain genes were present. The introduced beta-chain gene is transcriptionally active in two L cell clones examined whereas no transcription of the alpha-chain gene could be detected in the same transformants.

DNA↗
PubMed1987

Orientation and molecular map position of the complement genes in the mouse MHC.

Over the past few years six gene clusters have been isolated from the major histocompatibility complex (MHC) of the BALB/c mouse encompassing a total of 1600 kb of DNA and 48 genes. The molecular distances between these gene clusters and the orientation of four of the six clusters on chromosome 17 is not known. Here we use pulse-field gradient gels and Southern blot hybridization to establish large-scale genomic restriction maps covering several hundreds of kb surrounding the three gene clusters located in the K, I, S, and D regions of the MHC. Comparison of the maps orients the complement gene clusters in the S region with the 21-OHB gene pointing towards the K end and the C2 gene pointing towards the D end of the MHC. The distances between the E alpha and 21-OHB genes is 430 kb and between the C2 and TNF-alpha genes at least 420 kb.

Animals↗
PubMed1987

Cloning and preliminary characterization of the sacS locus from Bacillus subtilis which controls the regulation of the exoenzyme levansucrase.

The regulation of sacB, the gene encoding Bacillus subtilis levansucrase is altered by mutations located in several loci unlinked to sacB. Amongst these, the sacS locus seems to play an important role in the induction of sacB by sucrose. We have cloned sacS and found evidence suggesting that it contains two genes. The product of the first gene might repress the expression of the second; the second gene encodes a positive regulator of levansucrase synthesis, since its deletion abolishes this synthesis. There is a palindromic sequence resembling Q-independent terminators between the sacB promoter and the structural gene. Mutations affecting this palindrome make sacB constitutive. This suggests that the putative terminator is involved in the induction of sacB by sucrose. We discuss the possibility that the sacS-encoded positive regulator is a sucrose-dependent antiterminator which modulates transcription termination between the sacB promoter and the structural gene.

Bacillus subtilis↗
PubMed1987

Phosphoenolpyruvate:sugar phosphotransferase system of Bacillus subtilis: cloning of the region containing the ptsH and ptsI genes and evidence for a crr-like gene.

The genes ptsI and ptsH, which encode, respectively, enzyme I and Hpr, cytoplasmic proteins involved in the phosphoenolpyruvate:sugar phosphotransferase system, were cloned from Bacillus subtilis. A plasmid containing a 4.1-kilobase DNA fragment was shown to complement Escherichia coli mutations affecting the ptsH and ptsI genes. In minicells this plasmid expressed two proteins with the molecular weights expected for Hpr and enzyme I. Therefore, ptsH and ptsI are adjacent in B. subtilis, as in E. coli. In E. coli a third gene (crr), involved in glucose translocation and also in catabolite repression, is located downstream from the ptsHI operon. The 4.1-kilobase fragment from B. subtilis was shown to contain a gene that enables an E. coli crr mutant to use glucose. This gene, unlike the E. coli crr gene, was located to the left of ptsH.

Bacillus subtilis↗
PubMed1987

Gene transfer experiments to study T-cell recognition of MHC and antigen.

Gene transfer experiments are discussed which demonstrate the following: First, MHC-restricted antigen specificities of T lymphocytes are encoded by the alpha and beta T-cell receptor genes. Second, the interaction between cytotoxic T lymphocytes and their target cells is enhanced by the Lyt 2 molecule.

Animals↗