Cloning, expression of the human substance K receptor, and analysis of its role in mitogenesis.
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Biomedical subjects
Publications and source records attributed to C M Croce.
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Human mast cell growth factor (MGF) complementary DNAs (cDNAs) were cloned from HeLa cells using the polymerase chain reaction with oligonucleotides corresponding to murine and human MGF sequences. Sequencing of the cloned human MGF polymerase chain reaction products revealed two types of cDNA: a full length form corresponding in size to the murine cDNA, and an alternately spliced clone with a deletion of the sixth exon of the gene. Since membrane-bound MGF is predicted to be proteolytically cleaved within the sequences encoded by exon 6 to generate a soluble protein, this alternately spliced cDNA would likely encode a noncleavable, membrane-bound form of MGF. No difference in biological activity on human bone marrow cells was observed with recombinant, soluble forms of both types of human MGF protein. Our previous localization of the murine MGF gene to the Sl locus on chromosome 10 suggested (via conserved linkage groups) that the human MGF gene would be located on human chromosome 12. Therefore, rodent-human somatic cell hybrids with or without an entire human chromosome 12 and hybrids retaining partial 12 were tested by Southern blot analysis and used to show the presence of the human Mgf locus at chromosome region 12q. Chromosomal in situ hybridization localized the gene to 12q22-q24 in the region predicted by the comparative mapping of the murine Mgf/Sl locus.
The primary structure of the human substance K receptor was established from the sequences of complementary DNA clones isolated from a human jejunal complementary DNA library. It consists of 398 amino acids, including seven putative transmembrane regions. The gene for the human substance K receptor was localized to chromosome region 10p13-10q23, a region with frequent chromosomal abnormalities. The human substance K receptor was expressed in transfected NIH-3T3 cells lacking endogenous substance K receptors, and Scatchard analysis of 125I-labeled substance K binding indicates approximately 100,000 receptors/cell with a single dissociation constant of 12 nM. Covalent cross-linking experiments utilizing 125I-substance K and three different chemical cross-linking reagents (disuccinimidyl suberate, disuccinimidyl tartrate, or 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide-HCl) demonstrate an apparent molecular weight of 45,000, consistent with little or no N-linked glycosylation. The binding of substance K to its receptor on transfected cells led to a rapid increase in the production of total inositol phosphates and the release of Ca2+ from internal stores. Growth of the cells transfected with the human substance K receptor is stimulated by the addition of substance K to the medium to a level similar to 10% serum. Therefore, the human substance K receptor can function as a growth factor receptor when expressed in mouse 3T3 cells.
cDNA clones encoding zinc finger structures were isolated by screening Molt4 and Jurkat cDNA libraries with zinc finger consensus sequences. Candidate clones were partially sequenced to verify the presence of zinc finger-encoding regions; nonoverlapping cDNA clones were chosen on the basis of sequences and genomic hybridization pattern. Zinc finger structure-encoding clones, which were designated by the term "Kox" and a number from 1 to 32 and which were apparently unique (i.e., distinct from each other and distinct from those isolated by other laboratories), were chosen for mapping in the human genome. DNAs from rodent-human somatic cell hybrids retaining defined complements of human chromosomes were analyzed for the presence of each of the Kox genes. Correlation between the presence of specific human chromosome regions and specific Kox genes established the chromosomal locations. Multiple Kox loci were mapped to 7q (Kox 18 and 25 and a locus detected by both Kox 8 cDNA and Kox 27 cDNA), 8q24 5' to the myc locus (Kox 9 and 32), 10cen----q24 (Kox 2, 15, 19, 21, 30, and 31), 12q13-qter (Kox 1 and 20), 17p13 (Kox 11 and 26), and 19q (Kox 5, 6, 10, 22, 24, and 28). Single Kox loci were mapped to 7p22 (Kox 3), 18q12 (Kox 17), 19p (Kox 13), 22q11 between IG lambda and BCR-1 (locus detected by both Kox 8 cDNA and Kox 27 cDNA), and Xp (Kox 14). Several of the Kox loci map to regions in which other zinc finger structure-encoding loci have already been localized, indicating possible zinc finger gene clusters. In addition, Kox genes at 8q24, 17p13, and 22q11--and perhaps other Kox genes--are located near recurrent chromosomal translocation breakpoints. Others, such as those on 7p and 7q, may be near regions specifically active in T cells.
The role of bcl-2 in the signal transduction pathway was assessed by studying the inositol phospholipid metabolism in fibroblasts transfected by this oncogene. The rate of accumulation of water soluble inositol phosphates in response to several growth factors was much higher in bcl-2 transfected NIH3T3 clones than in untransfected control. Moreover, bcl-2 transfected clones express elevated levels of phosphatidic acid, a phospholipid produced during receptor stimulated breakdown of phosphoinositides. Our findings suggest that the expression of bcl-2 in NIH3T3 fibroblasts leads to the coupling of growth factor receptors to stimulate inositol phosphate production, henceforth establishing its role in the growth factor receptor mediated signal transduction pathway.
The structure of the c-myc locus and the flanking chromosomal region was investigated by Southern blot analysis of DNA from bone marrow aspirates from 42 patients with multiple myeloma. The main abnormality detected was the rearrangement of the MLVI-4 locus, 20 kilobases 3' of c-myc, which was observed in seven cases (16%). Two of these rearrangements were detected at the time of the initial diagnosis, four during treatment, and one at relapse, and their presence correlated with unresponsiveness to therapy. The MLVI-4 locus represents the human homologue of the Moloney leukemia virus integration-4 locus (Mlvi-4), a common region for provirus integration in Moloney murine leukemia virus-induced T-cell lymphomas in rodents. Provirus integration in this locus activates c-myc, and two additional genes, Mlvi-4 and Mlvi-1. The c-myc gene was rearranged in one patient; mutations involving the first exon of c-myc, frequently detected by altered restriction enzyme recognition sites in Burkitt's lymphomas, were not observed in these myelomas.
Antisense oligodeoxynucleotides specific for sequences in mRNAs from the B-cell lymphoma/leukemia-2 (BCL2) gene were used to inhibit the growth in culture of a human leukemia cell line, 697. Normal phosphodiester (PO) and nuclease-resistant phosphorothioate (PS) oligodeoxynucleotides were compared with regard to specificity, potency, and kinetics. Both PO and PS antisense BCL2 oligodeoxynucleotides were specific inhibitors of cellular proliferation, since sense versions of these synthetic DNAs were inactive at similar concentrations. Specificity was further confirmed by quantitative immunofluorescence studies, showing that PO and PS antisense BCL2 oligodeoxynucleotides (when used at appropriate concentrations) reduced levels of BCL2 protein without influencing expression of HLA-DR and other control antigens. The onset of inhibition by PO oligodeoxynucleotides was faster, with reductions in cell numbers occurring within 1 day of addition to cultures, in contrast to phosphorothioates, which were ineffective until 3-4 days. Phosphorothioates were more potent that phosphodiesters, however, with half-maximal inhibition of leukemic cell growth occurring at concentrations 5-10 times lower. As expected from previous studies demonstrating the importance of BCL2 for regulating lymphoid cell survival, BCL2 antisense oligodeoxynucleotides also led to 697 leukemic cell death through sequence-specific mechanisms, with reductions in cellular viability generally lagging the inhibitory effects on cellular growth by about 2 days. Taken together, these data indicate that PO and PS oligodeoxynucleotides targeted against the human BCL2 protooncogene can be sequence-specific inhibitors of leukemic cell growth and survival.
Early relapse and minimal residual disease during clinical remission was examined in two patients having acute T-cell leukemia/lymphoma with the t(10;14)(q24;q11) chromosomal translocation. Molecular probes which can detect T-cell receptor alpha/delta clonal rearrangements and a TCL-3 probe which can detect the clonal rearrangement due to the chromosomal translocation failed to detect the leukemic clones during clinical remission by Southern filter hybridization. However, application of the polymerase chain reaction technology in amplification of the t(10;14)(q24;q11) chromosomal juncture during clinical remission permitted us to increase the detection level of neoplastic cells up to 1 leukemic cell/125,000 normal cells using 1 microgram of DNA. Amplified junction fragments were detected in both patients. In one case, during the period of clinical remission no amplified fragments were detected.
We have analyzed the molecular features of a t(11;14)(q23;q32) chromosome translocation of a cell line established from a B-cell lymphoma. Somatic hybrid cells carrying the 11q- and/or 14q+ chromosome(s) were produced in order to map the breakpoints. Southern blot analyses of DNAs from these hybrid cell lines together with various probes from the IGH locus on chromosome 14 and the ETS-1 and CD3 genes on chromosome 11 showed that the breakpoints of the translocation occurred between the constant regions of the C phi gamma and C gamma 2 genes on chromosome 14 and between the CD3 and ETS-1 genes on chromosome 11. The t(11;14)(q23;q32) translocation does not seem to involve the same mechanism that is responsible for translocations occurring at the immunoglobulin heavy chain joining segment (JH).
T cell somatic hybrids were obtained by fusion of human tetanus toxoid-specific gamma + delta + T cells and a T cell lymphoma cell line that expresses beta-chain but not alpha-chain transcripts. The hybrids simultaneously and independently expressed alpha beta and gamma delta TCR heterodimers on the cell surface without any significant differences in the level of expression. No heterodimers containing alpha delta-, beta delta-, beta gamma-, and alpha gamma-chains were transported to the cell membrane, indicating a chain specificity in dimer formation. The presence of productively rearranged gamma- and delta-alleles in the hybrid cells and immunoprecipitation of an identical type of TCR-gamma delta from both hybrid and parental gamma + delta + T cells suggests that TCR-gamma delta on the hybrid cells derives from gamma + delta + T cells. Anti-TCR (TCS-delta 1 or WT31) and anti-CD3 antibodies induced a rapid increase in [Ca2+]i in the double-positive hybrids and their variants positive for either the alpha beta or gamma delta complex. Double positive hybrid cells were refractory to stimulation with anti-CD3 antibody after pretreatment with a mixture of anti-TCR-gamma delta and anti-TCR-alpha beta antibodies but not with either antibody alone indicating the functional independence of the two receptors. However, only gamma delta heterodimer receptor was able to respond to tetanus toxoid presented on autologous APC as measured by induction of the p55 chain of IL-2R on stimulated cells.
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The finger motif is a tandemly repeated DNA-binding domain recently identified in the primary structure of several eukaryotic transcriptional regulatory proteins. It has been proposed that some members of the finger-gene family are implicated in both normal cell proliferation and differentiation. We isolated several human finger genes by means of hybridization with a finger motif-containing DNA probe. One of these finger genes, HF.10, is expressed at low levels in a variety of human tissues and is down-regulated during the in vitro terminal differentiation of human leukemic myeloid cell lines. By in situ hybridization experiments and analysis of interspecific somatic cell hybrids we mapped the HF.10 gene to 3p21-22, a chromosome region frequently involved in karyotypic rearrangements associated with lung and renal cancer.
We have isolated cDNA clones from a human NK cell cDNA library that encode the serine protease granzyme B. Although the sequence of the entire coding region for the mature protein and the 3' untranslated region of the clone are identical to other cDNA isolates of this gene obtained from human T cell cDNA libraries, the 5' end of two clones is 103 bp longer than the previously described sequences and would encode a protein with a 54-amino-acid-long signal sequence. Experiments characterizing granzyme B mRNA suggest that transcripts that initiate at or before the 5' end of these clones comprise a detectable but infrequent class of granzyme B transcripts in NK and T cells. We have mapped this gene to human chromosome 14 in the region 14q11----14q32, distal to the T cell receptor alpha locus and proximal to the immunoglobulin heavy chain locus. The chromosomal location of this gene, together with the previously described high sequence homology between this gene and the mouse CTLA 1/ccp1 gene, make it likely that this is the human equivalent of the mouse CTLA1/ccp1.
A novel human oncogene, designated VAV, has been recently characterized. This oncogene was generated by a rearrangement within the 5' coding sequences of a normal cellular gene, the VAV proto-oncogene. The normal VAV gene is specifically expressed in hematopoietic cells regardless of their differentiation lineage. We now report that the VAV locus has been localized in the human genome at chromosome 19p12----19p13.2 by analysis of its segregation pattern in rodent-human somatic cell hybrids and by chromosomal in situ hybridization. The VAV locus might be closely linked to the insulin receptor (INSR) locus, as suggested by comigration of INSR and VAV high-molecular-weight DNA fragments after pulsed-field gel electrophoresis. The VAV chromosomal assignment is of interest because chromosome region 19p13 is involved in different karyotypic abnormalities in a variety of malignancies including melanomas and leukemias. The identification of a novel proto-oncogene that maps to that region will enable us to define whether VAV is involved in any of the translocations observed.
Despite little sequence homology other than the GDP/GTP binding region, bcl-2 and ras proteins behave in similar fashion in many physiological and biochemical aspects. Both of them are toxin insensitive, small Mr G-proteins attached to the inner surface of the cell membrane with autophosphorylation activity and can cooperate with c-myc in cell transformation. In the case of bcl-2, however, the mechanism of activation is still unclear. One possibility is that, following antigen or mitogen stimulation, the bcl-2 protein is activated by nucleotide exchange; then the activated bcl-2 protein may interact with some other protein in the signal transduction pathway leading to cell proliferation. Dissection of the role of bcl-2 in the regulation of B-cell proliferation will be an important step in understanding its role in the pathogenesis of B-cell neoplasia.
Erythropoietin (EPO), the primary regulator of mammalian erythropoiesis, binds and activates a specific receptor on erythroid progenitors. The human and mouse cDNAs for this receptor (EPOR) have recently been isolated. These cDNAs were used to establish the genomic location of the EPOR gene. By somatic cell hybrid analysis, the locus for the EPOR maps to human chromosome (Chr) 19pter-q12. By interspecific backcross mapping the locus is tightly linked to the murine Ldlr locus near the centromere of mouse Chr9. This region of mouse Chr9 is homologous to a region of human Chr 19p13 carrying the human LDLR and MEL loci, strongly suggesting that the human EPOR gene is at 19p13 near the human LDLR locus.
The human ARH genes (previously called RHO) share several properties with the ras gene family. Three members of the ARH family, the H6, H9, and H12 genes, have been localized to human chromosomes 2, 5, and 3, respectively. Analysis of DNAs from a rodent-human somatic cell hybrid panel demonstrates linkage of H6 to chromosome region 2p12----2pter and H9 to region 5q33----5qter. In situ chromosome hybridization also showed that the primary site for H9 is in the 5q31----qter region. The H12 gene was some-what difficult to localize using rodent-human hybrids because the probe detects a family of rodent genes as homologous to the human probe as in the human cognate gene. However, chromosome in situ hybridization revealed grains clustered in region 3p14----3p22 with a significant peak in band 3p21. We conclude that H6 is in 2p12----pter, H9 in 5q31----5qter, and H12 in 3p21.
Chromosome studies are helping to identify oncogenes, both known and previously unknown, involved in the pathogenesis of human lymphocytic tumors; and mechanisms by which the function of these genes is critically altered. Most extensively studied have been the chromosome translocations involving the myc gene in Burkitt's lymphomas and the bcl-2 gene in low-grade lymphomas, where "activation" of the oncogene results from association with a transcriptionally active immunoglobulin gene. Other putative oncogenes, similarly involved in translocations with immunoglobulin genes (in B-cell tumors) or T-cell receptor genes (in T-cell tumors), are currently being investigated, as well as alternative mechanisms of myc gene activation in these neoplasms. Limited clinical applications of these studies have already been forthcoming, and they should eventually lead to improvements in diagnosis, prognosis, and even therapy.