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K Ganguly

Publications and source records attributed to K Ganguly.

15 recordsLinked to original sources
PubMed1995

AT-rich upstream sequence elements regulate spore germination-specific expression of the Dictyostelium discoideum celA gene.

Two members of a family of spore germination-specific cDNAs, celA and celB, are expressed coordinately, exclusively during spore germination. In the present study the regulatory sequence elements responsible for celA germination-specific expression have been identified. The very AT-rich 81 bp sequence between -664 and -584 upstream of the translation initiation site was required for proper temporal transcription of the celA gene. This sequence is comprised of two cis elements, each of which was active by itself in allowing celA expression. Electrophoretic mobility shift assays showed that a factor(s) in an extract prepared from germinating spores bound to the celA regulatory region. One of the three complexes formed was specific for the germinating spore extract. The results are consistent with the notion that the factor(s) that binds to this regulatory region is involved in expression of celA.

Animals↗
PubMed1992

Retrovirus transformation associated secretory phosphoproteins of mouse and mink cells.

Using antisera to major excreted protein (MEP) of Kirsten sarcoma virus transformed NIH 3T3 (KNIH) cells, we have identified phosphoproteins from the media of feline sarcoma virus (FeSV) transformed mink cells. These secretory phosphoproteins from FeSV-transformed mink cells are of 35 kDa M.W. and they do not have autophosphorylation activity. A comparative analysis of MEP from the media of transformed mouse and mink cells was performed on the basis of proteolytic cleavage products and acid hydrolyzed products of the phosphoproteins. While a marked difference was observed in the peptide map, a common 32P-linked molecule was observed following acid hydrolysis of both species of phosphoproteins.

3T3 Cells↗
PubMed1987

Comparison of recombinant human immunodeficiency virus gag precursor and gag/env fusion proteins and a synthetic env peptide as diagnostic reagents.

Diagnostic reagents for detection of human immunodeficiency virus (HIV) exposure with improved reliability may be provided by viral encoded proteins produced by recombinant DNA techniques or by synthetic peptides corresponding to appropriate viral epitopes. We have expressed at high levels in E. coli a gag gene segment corresponding to approximately 97% of the p55 gag precursor protein, as well as a novel gag/env fusion protein that contains antigenic determinants in common with gag p24, env gp41, and env gp120. The gag and gag/env proteins were purified from insoluble inclusion bodies by sequential extraction with increasing concentrations of urea. These components were tested for reactivity with antisera to HIV proteins and peptides. We have also chemically synthesized a peptide corresponding to env residues 578-608, representing a portion of env gp41. The final preparation of gag and gag/env proteins in 8 M urea reacted with sheep anti-HTLV-III p24 gag antibodies and acquired immune deficiency syndrome (AIDS) patient sera. The gag/env fusion protein also reacted with rabbit anti-HIV env 500-511 peptide antibody. Both recombinant proteins and the env peptide were suitable as reagents for evaluation of serum samples by enzyme-linked immunosorbent assay (ELISA). Results of ELISA assays utilizing the recombinant viral proteins and synthetic peptide were in good agreement with results obtained using disrupted virus as antigen in ELISA assays and immunoblotting.

Acquired Immunodeficiency Syndrome↗
PubMed1986

HTLV-III gag protein is processed in yeast cells by the virus pol-protease.

The gag-pol gene of HTLV-III (human T-lymphotropic virus), the virus linked to AIDS (acquired immune deficiency syndrome), was expressed in yeast, and processing of the gag precursor into proteins of the same size as those in the virion was observed. Processing of the gag gene in yeast cells mimics the process that naturally occurs in mammalian cells during maturation of virions. Therefore it was possible to perform mutational analysis of the virus genome to localize the gene that codes for the protease function to the amino terminal coding region of the pol gene. Since this region overlaps the gag gene, it is likely that ribosomal frameshifting occurs from gag to pol. Antibodies in all of the AIDS patients' sera tested recognized the yeast synthesized gag proteins, although the sera showed differences in relative reactivity to the individual gag proteins and the precursor. This yeast system should be valuable not only for production of viral proteins for diagnostic or vaccine purposes but also for analysis of the genetics and biochemistry of viral gene functions--parameters that are difficult to study otherwise with this virus.

Acquired Immunodeficiency Syndrome↗
PubMed1986

Dissociation of cellular transformation from platelet-derived growth factor independence.

ST2-3T3, a spontaneously transformed BALB/c-3T3 cell line which does not require platelet-derived growth factor (PDGF) for growth, was fused to THO2, a PDGF-responsive non-transformed BALB/c-3T3 cell line, in order to learn whether transformation is expressed coordinately with PDGF independence. Hybrid cells were selected and grown in medium containing both HAT (hypoxanthine-aminopterin-thymidine) and ouabain; unfused cells of each parental type were killed in HAT-ouabain medium. Five independently isolated ST2-3T3xTHO2 hybrid cell lines were established and characterized for both transformation and PDGF responsiveness. All five were transformed, having a disorganized growth pattern and achieving a final cell density similar to that of ST2-3T3 cells. Two of these lines did not respond to a brief treatment with PDGF: the mitogen neither induced the synthesis of a PDGF-modulated lysosomal protein (termed MEP), nor stimulated the cells to enter the S phase; one line responded to PDGF by synthesizing both MEP and DNA, whereas two others synthesized MEP but not DNA. In contrast, four independently isolated cell lines obtained by fusing PDGF-responsive non-transformed BALB/c-3TC cells to the THO2 line were all PDGF-responsive for both MEP and DNA synthesis and were not transformed. It appears that PDGF independence is not required for the transformation of BALB/c-3T3 cells.

Animals↗
PubMed1985

HTLV-III env gene products synthesized in E. coli are recognized by antibodies present in the sera of AIDS patients.

The envelope gene of HTLV-III, the retrovirus directly linked to AIDS, encodes a protein of 856 amino acids. Our sequence analysis of the cloned HTLV-III (HXB-3) env gene and its comparison with other isolates reveal significant divergence, especially in the external portion of this protein. A large segment of the env gene (1800 bp) was inserted into the expression vector pEV-vrf3, and a corresponding 68 kd protein, which encompasses both the extracellular and the membrane-associated regions of the native protein, was produced in E. coli. Several smaller polypeptides, which appear to be internal initiation products, were also produced. All 50 AIDS patient sera obtained from different locations in the United States specifically recognized the bacterially synthesized envelope proteins, as judged by Western blots. This suggests that these proteins will be useful for the diagnosis of HTLV-III infection and possibly as a vaccine against AIDS.

Acquired Immunodeficiency Syndrome↗
PubMed1985

Feline leukemia virus-and feline sarcoma virus-related polypeptides released by virus producer and nonproducer cells.

Polypeptides specific for feline leukemia virus (FeLV) have been identified in the media of cells that produce FeLV as well as in nonproducer cells transformed by feline sarcoma viruses (FeSV). Cat fibroblasts that were persistently infected with FELV release the major virus envelope glycoprotein, whereas cultured cat lymphoma cells shed both glycopeptides related to the virus core gene (gag) and glycopeptides related to the virus envelope gene (env). Mink cells and cat cells transformed by FeSV secrete polypeptides of a wide range of sizes that cross-react with the major virus core protein p27. Differences in the classes of p27-related proteins produced may be related to the strain of virus and the cell type. Cat cells transformed by FeSV release a glycopeptide that appears to be processed differently from those identified in the media of FeSV-transformed mink cells. The possibility that such FeLV-related secretory proteins may interfere with the immune response of the host is discussed.

Animals↗
PubMed1983

Analysis of the interaction between Rauscher murine leukemia virus and murine cell membrane receptor by in vitro binding assay.

Binding of 125I-labeled gp70 of Rauscher murine leukemia virus (R-MuLV) by 3 murine cell lines, BALB/c-3T3, NIH/3T3 and KA-31 (Kirsten murine sarcoma virus transformed clone A-31 of BALB/c-3T3) cells was measured. The binding was a saturable process, dependent on the concentration of gp70 and on the number of cells. In no experiment could we demonstrate any quantitative utilization of gp70 in the medium. However, gp70 remaining in the spent medium could be bound to fresh cells in a subsequent incubation. BALB/c-3T3, NIH/3T3 and KA-31 cells showed similar association constants (1.2-2.5 x 10(8) M-1) for the binding. Moreover, all 3 cell lines had similar number of receptors (7.4-8.9 x 10(5)) per cell. Neither N- and B-tropism of the cells nor transformation by a sarcoma virus altered the number and type of the cell surface receptors.

Animals↗
PubMed1983

Cell surface receptors for ecotropic murine viruses are different from those for xenotropic and amphotropic viruses.

The murine cell surface receptor for Rauscher murine leukemia virus was analyzed using a binding assay involving cultured murine cells and 125I-labeled envelope glycoprotein, gp70, of the virus. The binding was competitively inhibited by extracts of ecotropic murine viruses. No inhibition was observed with a xenotropic or an amphotropic murine type-C virus, a murine type-B virus, and several nonmurine retroviruses. Unlike cells producing ecotropic murine viruses, murine cell lines actively producing either an endogenous xenotropic virus or an amphotropic virus showed a significant degree of receptor activity for Rauscher murine leukemia virus gp70. When murine cells were induced with iododeoxyuridine to produce a xenotropic virus and an ecotropic virus in distinct phases, the receptor activity of the induced cells remained unchanged during xenotropic virus release, but a dramatic decrease was evident with the onset of ecotropic virus release. These findings show that ecotropic murine viruses share a common receptor on the murine cell surface and that this receptor is distinct from those for xenotropic and amphotropic murine viruses.

Animals↗