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Biomedical subjects

C Birchmeier

Publications and source records attributed to C Birchmeier.

65 records · Page 4Linked to original sources
PubMed1987

Human ros1 and mas1 oncogenes located in regions of chromosome 6 associated with tumor-specific rearrangements.

Oncogenes have been implicated in tumorigenesis based on their localization to chromosomal sites associated with tumor-specific structural rearrangements. We have mapped the human ros1 (formerly mcf3) and mas1 oncogenes to the distal half of chromosome 6q, within a region frequently rearranged in malignant cells. Chromosomal mapping of these two new human transforming genes may help elucidate the involvement of the long arm of chromosome 6 in diverse tumor types.

Cell Line↗
PubMed1986

Isolation and characterization of a new cellular oncogene encoding a protein with multiple potential transmembrane domains.

We have cloned and sequenced a new human oncogene and have named it mas. This oncogene was detected by its tumorigenicity in nude mice using the cotransfection and tumorigenicity assay previously described. The mas oncogene has a weak focus-inducing activity in transfected NIH 3T3 cells. A DNA rearrangement in the 5' noncoding sequence, which occurred during transfection, is probably responsible for activation of the mas gene. The cDNA sequence of the mas oncogene reveals a long open reading frame that codes for a 325 amino acid protein. This protein is very hydrophobic and has seven potential transmembrane domains. In this respect, the structure of the mas protein is novel among cellular oncogene products and may reflect a new functional class of oncogenes.

Animals↗
PubMed1986

Characterization of an activated human ros gene.

A human oncogene, mcf3, previously detected by a combination of DNA-mediated gene transfer and a tumorigenicity assay, derives from a human homology of the avian v-ros oncogene. Both v-ros and mcf3 can encode a protein with homology to tyrosine-specific protein kinases, and both mcf3 and v-ros encode a potential transmembrane domain N terminal to the kinase domain. mcf3 probably arose during gene transfer from a normal human ros gene by the loss of a putative extracellular domain. There do not appear to be any other gross rearrangements in the structure of mcf3.

Amino Acid Sequence↗
PubMed1986

Exploring the function of RAS oncogenes by studying the yeast Saccharomyces cerevisiae.

The RAS oncogenes comprise a family of genes found to be activated in perhaps 10-20% of human cancers and which have been highly conserved in evolution. Homologs of the mammalian RAS exist in the yeast Saccharomyces cerevisiae (RAS1 and RAS2). We have shown that human ras proteins can complement the loss of RAS1 and RAS2 proteins in yeast, and hence are functionally homologous. Both human and yeast RAS proteins can stimulate the magnesium and guanine nucleotide-dependent adenylate cyclase activity present in yeast membranes. However, RAS proteins do not appear to stimulate adenylate cyclase in vertebrate cells. Our studies indicate that although RAS proteins are essential controlling elements of adenylate cyclase in yeast, they have other essential functions in that organisms. RAS proteins are themselves probably controlled by growth regulatory proteins.

Fungal Proteins↗
PubMed1985

ras proteins can induce meiosis in Xenopus oocytes.

Injection of human H-ras protein induces maturation of Xenopus oocytes; that is, progression from prophase to metaphase of meiosis. The oncogenic protein encoded by H-rasval12 is nearly a 100-fold more potent than the protein encoded by the wild-type gene. We do not observe any measurable increase or decrease in cyclic AMP concentration in injected oocytes, and the effects of H-ras protein are only partially blocked by cholera toxin. Our results suggest that not all, if any, of the effects of H-rasval12 protein in this system are mediated by adenylate cyclase.

1-Methyl-3-isobutylxanthine↗
PubMed1984

3' editing of mRNAs: sequence requirements and involvement of a 60-nucleotide RNA in maturation of histone mRNA precursors.

In vitro-synthesized transcripts of the sea urchin histone H2A gene with 3' extensions are efficiently and rapidly processed to H2A mRNA with faithful 3' ends in Xenopus laevis oocyte nuclei. Processing requires the presence of a histone-specific dyad symmetry element and of H2A-proximal spacer sequences in the precursor RNA. In DNA injection experiments with a processing-deficient H2A mutant, the transcription products appear to terminate heterogeneously in the first 100-200 base pairs of the post-H2A spacer. Processing of synthetic H3 RNA precursors requires the prior injection of a 60-nucleotide RNA from sea urchin embryos that seems to be a component of a small nuclear ribonucleoprotein.

Animals↗
PubMed1983

The terminal RNA stem-loop structure and 80 bp of spacer DNA are required for the formation of 3' termini of sea urchin H2A mRNA.

We have studied the exact sequence requirement for the formation of 3' termini of the sea urchin H2A mRNA in frog oocyte injection experiments. Point mutations destroying the symmetry of the inverted DNA repeat in the mRNA trailer coding sequences prevent the generation of genuine 3' termini. Mutants containing complementary base changes are pseudorevertants and allow the production of H2A mRNA with faithful 3' termini at wild-type levels. Our transcription analyses show that it is primarily the sequence of the transcribed strand that decides whether or not true 3' mRNA termini are produced. This is evidence that an RNA stem-loop structure, rather than a DNA cruciform, is essential for this process. Spacer sequences are absolutely required, because in their absence only H2A mRNA with spacer transcript extensions are found. Once the canonical CAAGAAAGA and flanking sequences are linked to the H2A gene, H2A messenger is synthesized at a suboptimal rate, which can be increased to wild-type levels by the addition of 80 bp of the spacer immediately adjacent to the H2A gene.

Animals↗
PubMed1982

Generation of authentic 3' termini of an H2A mRNA in vivo is dependent on a short inverted DNA repeat and on spacer sequences.

We have determined what sequences are required to generate the authentic 3' termini of a sea urchin H2A histone mRNA. We have constructed a series of deletion and insertion mutants in the cloned histone repeat unit h22 of Psammechinus miliaris and have analyzed the transcripts of both wild-type and mutant DNAs produced in the frog oocyte. The protein-coding sequences of the H2A gene can be removed without any deleterious effects on transcription initiation or termination. A 12 bp deletion, which removes a highly conserved inverted DNA repeat immediately preceding the H2A mRNA 3' terminus, elicits read-through of the polymerase into the spacer DNA further downstream. However, the inverted repeat and the sequence coding for the 3' terminus of the mRNA are by themselves not sufficient to generate faithful 3' ends. Our data suggest that spacer sequences downstream of the 3' mRNA terminus are required as well.

Animals↗
PubMed1980

Corrugated attachment membrane in WI-38 fibroblasts: alternating fibronectin fibers and actin-containing focal contacts.

The distributions of both fibronectin (LETS, CSP) fibers and focal contacts to the substratum, as viewed by fluorescence and reflection contrast microscopy, respectively, have been compared in freshly plated WI-38 human fibroblasts. Most frequently, the actual focal attachment plaques did not contain fibronectin fluorescence and, furthermore, fibronectin spots and fibers often alternated with focal contacts. Overlap, however, was observed between focal contacts and the endings of actin-containing stress fibers [see also Wehland, J., Osborn, M. & Weber, K. (1979) J. Cell Sci. 37, 257-273]. Thus, the fibroblast attachment membrane might best be described as a corrugated sheet that undulates between alternating microfilaments and fibronectin fibers, at the points of closest and farthest distance to the substratum, respectively.

Actins↗