Abstract. The recent cloning of complete cDNAs encoding carcinoembryonic antigen (CEA) and nonspecific cross-reacting antigen has revealed the existence of a new gene family belonging to the immunoglobulin gene superfamily. We have reported the isolation of a partial CEA cDNA and of L-cell transfectant cell lines that express human antigens cross-reactive with commercial antibodies directed to native CEA (Kamarck, M., J. Elting, J. Hart, S. Goebel, P. M. M. Rae, J. Nedwin, and T. Barnett. 1987. Proc. Natl. Acad. Sci. USA. 84:5350-5354). In this study, we describe the identification and cloning of 3.9-, 3.7-, 2.2-, and 1.8-kb cDNAs and a 23-kb genomic transcription unit, which code for new members of the CEA gene family. DNA sequence analysis of these cloned DNAs establishes the existence of a set of four alternatively spliced mRNAs which are expressed in several tumor cell lines, in human fetal liver, and in L-cell transfectants. Deduced amino acid sequences of the encoded isoantigens show extensive similarity to CEA and nonspecific cross-reacting antigens, but in addition demonstrate transmembrane and cytoplasmic domains. We designate members of this antigen family transmembrane' CEAs. The transmembrane CEA isoantigens share general structural characteristics with members of the immunoglobulin gene superfamily and can be specifically compared to the cell adhesion molecules, N-CAM (neural cell adhesion molecule) and MAG (myelin-associated glycoprotein).
Tobacco (Nicotiana tabacum) and soybean (Glycine max) tissue culture cells were exposed t o a heat shock and protein synthesis studied by SDS-polyacrylamide gel electrophoresis after labeling with radioactive amino acids. A new pattern of protein synthesis is observed in heat-shocked cells compared t o that in control cells. About 12 protein bands, some newly appearing, others synthesized in greatly increased quantities in heat-shock cells, are seen. Several of the heat-shock proteins (HSPs) in both tobacco and soybean are similar in size. One of the HSPs in soybean (76K) shares peptide homology with its presumptive 25°C counterpart, indicating that the synthesis of at least some HSPs may not be due to activation of new genes. The optimum temperature for maximal induction of most HSPs is 39-40°C. Total protein synthesis decreases as heatshock temperature is increased and is barely detectable at 45°C. The heatshock response is maintained for a relatively short time in tobacco cells. After 3 hr at 39"C, a decrease is seen in the synthesis of the HSPs, and after 4 hr practically n o HSPs are synthesized. After exposure t o 39°C for 1 hr, followed by a return of tobacco cells t o 26"C, recovery t o the control pattern of synthesis requires greater than 6 hours. These results indicate that cells of flowering plants exhibit a heat-shock response similar t o that observed in animal cells.Key words: heat-shock, proteins, tobacco, soybeanThe exposure of cells of several different animal species t o heat-shock, ie, a sudden increase in the incubation temperature, results in the inhibition of synthesis of most cell proteins and in the new synthesis of a relatively few proteins. This phenomenon has been extensively described for Drosophila [ 1 , 2 ] , as well as for other insects [3] and in avian and mammalian cells [4].
80% [5]) while retaining the characteristic Ig-like folds. The overall Ig-like character imparted to BGP molecules suggests that they function as receptors, perhaps involved in adhesion (23, 37). However, the alternate splicing of the extracellular IIa domain, in combination with two possible intracellular forms, one of which may be phosphorylated (1), suggests that alteration in these molecular structures could play an important role in recognition and signal transduction. Similar observations gave been made for other Ig-like molecules, most notably the fibroblast growth factor receptor (15,25,29).Defining the size and diversity of the BGP family is a first step in exploring a functional role. Toward this end, we surveyed the RNAs of many different normal tissues and transformed cell lines by polymerase chain reaction (PCR) amplification of the specific extracellular and intracellular regions of BGP mRNAs that are known to be alternatively spliced and code for one of several isoforms. By this process, we found additional size classes of amplified products that differ substantially from those previously described. Further characterization of these segments revealed that they code for two novel non-Ig-like extracellular domains derived by alternative splicing fromAlu-like elements, as well as another form that codes for a BGP isoantigen with only an N terminus anchored via a TM domain to a cytoplasmic tail. Some of these forms appear to be represented more in RNAs from tumor-derived cells than in RNAs from normal tissue counterparts, suggesting that the transformed phenotype may contribute to the appearance of new BGP splice variants and their translated polypeptides.The finding of additional novel forms of BGP extends the
Twelve research groups participated in the ISOBM TD-3 Workshop in which the reactivity and specificity of 83 antibodies against prostate-specific antigen (PSA) were investigated. Using a variety of techniques including cross-inhibition assays, Western blotting, BIAcore, immunoradiometric assays and immunohistochemistry, the antibodies were categorized into six major groups which formed the basis for mapping onto two- and three-dimensional (2-D and 3-D) models of PSA. The overall findings of the TD-3 Workshop are summarized in this report. In agreement with all participating groups, three main antigenic domains were identified: free PSA-specific epitopes located in or close to amino acids 86–91; discontinuous epitopes specific for PSA without human kallikrein (hK2) cross-reactivity located at or close to amino acids 158–163; and continuous or linear epitopes shared between PSA and hK2 located close to amino acids 3–11. In addition, several minor and partly overlapping domains were also identified. Clearly, the characterization of antibodies from this workshop and the location of their epitopes on the 3-D model of PSA illustrate the importance of selecting appropriate antibody pairs for use in immunoassays. It is hoped that these findings and the epitope nomenclature described in this TD-3 Workshop are used as a standard for future evaluation of anti-PSA antibodies.
Biliary glycoprotein (BGP) isoantigens are derived by alternative splicing from a single gene and are the human homologs of rat C-CAM and the mouse Bgp species. These glycoproteins represent a family of cell-adhesion molecules. The mouse Bgp isoforms also act as receptors for the hepatitis viral capsid-protein. BGP is a member of the carcinoembryonic antigen (CEA) gene family, which belongs to the immunoglobulin supergene family, yet it displays restricted expression patterns and unique functions. Since the loss or reduced expression of BGP is associated with human colorectal carcinomas, the elements in its upstream regulatory region were analyzed. A cluster of transcriptional initiation sites and the minimal promoter, located within 150 bp upstream of the major transcriptional start site, were active in human colon carcinoma and hepatoma cells. Unlike the CEA gene, BGP gene transcription was not modulated by a silencer region; repetitive elements in the BGP upstream region were not involved in activation or repression. Footprinting experiments identified two cis-acting elements and mobility-shift assays demonstrated that these elements bound several transcription factors, among them, USF, HNF-4 and an AP-2-like factor. In cotransfection experiments, both the USF and HNF-4 transcription factors transactivate the RGP gene promoter and compete for the same regulatory element. The Spl transcription factor, shown to be involved in CEA gene transcriptional regulation, does not bind to the BGP gene promoter. We, therefore, propose that the relative distributions and interactions of these transcription factors mediate distinct transcriptional regulation of the BGP gene in colon and liver; this regulation could be distorted during the oncogenic process.
The arrangement of repetitive and non-repetitive sequence was studied in the genomic DNA of the oyster (Crassostrea virginica), the surf clam (Spisula solidissima), the horseshoe crab (Limulus polyphemus), a nemertean worm (Cerebratulus lacteus) and a jelly-fish (Aurelia aurita). Except for the jellyfish these animals belong to the protostomial branch of animal evolution, for which little information regarding DNA sequence organization has previously been available. The reassociation kinetics of short (250-300 nucleotide) and long (2,000-3,000 nucleotide) DNA fragments was studied by the hydroxyapatite method. It was shown that in each case a major fraction of the DNA consists of single copy sequences less than about 3,000 nucleotides in length, interspersed with short repetitive sequences. The lengths of the repetitive sequences were estimated by optical hyperchromicity and S1 nuclease measurements made on renaturation products. All the genomes studied include a prominent fraction of interspersed repetitive sequences about 300 nucleotides in length, as well as longer repetitive sequence regions.
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