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Biomedical subjects

U Malipiero

Publications and source records attributed to U Malipiero.

26 records · Page 2Linked to original sources
PubMed1993

cDNA cloning of human N-Oct3, a nervous-system specific POU domain transcription factor binding to the octamer DNA motif.

Octamer transcription factors (Oct or OTF) are a subset of the POU family of transcription factors which regulate transcription of cellular and viral genes by binding to the octamer sequence motif ATGCAAAT. Neurons and astroglial cells harbour, in addition to the ubiquitous Oct 1 factor, at least four specific factors termed N-Oct 2,3,4 and 5. Here we report the cloning of a human brain-derived cDNA that encodes the N-Oct 3 protein (443 aa) which is the human counterpart of the murine brain-2 gene product. Extracts from mammalian cells transfected with an N-Oct 3 expression vector yield three octamer DNA binding complexes in the electrophoretic mobility shift assay (EMSA): N-Oct 3 and two smaller complexes comigrating with the N-Oct 5A and 5B proteins of brain extracts. We present data suggesting that the N-Oct 5A and 5B proteins are generated by alternative translation initiation at internal AUG residues which are located before the POU domain. In contrast to the putative N-Oct 5 proteins, which are transcriptionally inert, the N-Oct 3 protein activates transcription from a reporter gene promoter with an octamer sequence, when transiently expressed in HeLa cells.

Amino Acid Sequence↗
PubMed1992

Human small cell lung cancer expresses the octamer DNA-binding and nervous system-specific transcription factor N-Oct 3 (brain-2).

Small cell lung cancer (SCLC) cells express several characteristics of neuronal cells, including synthesis of neuropeptides and expression of the respective receptors. Establishment and maintenance of the neuronal phenotype of SCLC may depend on expression of gene transcription factors inherent to the central nervous system. The present study shows the nervous system-specific transcription factor N-Oct 3 (brain-2) to be expressed in all 13 SCLC cell lines investigated. Furthermore, N-Oct 3 (brain-2) was also found in SCLC-derived skin metastasis. In contrast, in extracts and RNA of non-SCLC cell lines and non-SCLC tumor tissues, such as lung squamous, large cell, and adenocarcinoma, expression of N-Oct 3 (brain-2) was not detectable. These data support the concept that SCLC cells derive from the neuroectodermal cell lineage since expression of N-Oct 3 (brain-2) protein is highly abundant at the neural tube stage and in the adult restricted to the neuroectodermal cell lineage.

Carcinoma, Small Cell↗
PubMed1992

Neurons and neuroblastoma as a source of macrophage colony-stimulating factor.

Accumulation of macrophages in brain tissue as observed in nervous system injury may be due to local production of hematopoietic colony-stimulating factors (CSF). The present work shows human neuroblastoma cells and murine neurons, namely granule cells of the cerebellum, to produce macrophage (M)-CSF which guides expansion and differentiation of macrophage lineage cells. The mRNA-encoding M-CSF but not the respective protein is present in mouse brain including cerebellum. Neither granulocyte M-CSF nor IL-3 is produced by cerebellar neurons or neuroblastoma. By their production of M-CSF, neurons may regulate the macrophage response and lead to local expansion and enhanced function of macrophages in inflammatory diseases of the central nervous system.

Animals↗
PubMed1992

Modulation of the immune response by transforming growth factor beta.

For the past several years immunologists have been fascinated by a series of experiments showing that transforming growth factor beta (TGF beta) suppresses T- and B-lymphocyte growth as well as IgM and IgG production by B cells. Moreover, while exerting chemotactic activity on monocytes and inducing expression of interleukin-1 and interleukin-6 by these cells, TGF beta interferes with bacterially induced tumor necrosis factor alpha production, oxygen radical formation and the adhesiveness of granulocytes to endothelial cells. These mechanisms may provide the basis for the effect of TGF beta to prevent the microvascular changes associated with brain edema formation in bacterial meningitis. Given the potential of lymphocytes as well as macrophages to produce TGF beta 1, this cytokine may exert negative feedback signals on the immune response, provided the cytokine is processed from its latent form to the bioactive homodimer. Potent effects of TGF beta have been observed in experimental animals including the inhibition of the generation of virus-specific cytotoxic T cells and antiviral antibodies as well as the diminution of cellular infiltrates with decreased major histocompatibility complex class-II expression and CD8+ T cells in the tissue of virally infected animals. TGF beta may also be of importance in tumor immunology. By the production of bioactive TGF beta as detected in glioblastoma and acute T-cell leukemia, tumor cells may induce an immunodeficiency state and escape immune surveillance. In inflammation, monitoring of TGF beta in the tissue will bring light on the immune regulation in acute and chronic inflammatory diseases.

Animals↗
PubMed1991

Expression of TGF-beta 2 in human glioblastoma: a role in resistance to immune rejection?

Glioblastomas are among the most malignant tumours for which no curative treatment exists. A dysfunction of cellular immunity with decreased skin reactivity and lymphocyte blastogenesis has been described in patients with glioblastomas. In culture human glioblastoma cells release a factor termed glioblastoma-derived T cell suppressor factor (G-TsF) which inhibits the antigen-dependent growth of both helper and cytotoxic T cells. Purification and cloning indicated that G-TsF is a novel member of the TGF-beta family with a well-conserved mature sequence but less homology in the precursor segments. The factor was renamed TGF-beta 2. The two glioblastoma cell lines investigated expressed mRNAs for both G-TsF/TGF-beta 2 and TGF-beta 1 but only G-TsF/TGF-beta 2 protein was secreted. Neuroblastoma cells express only the mRNA for TGF-beta 1 but not the protein, nor the mRNA for G-TsF/TGF-beta 2. Recombinant G-TsF/TGF-beta 2 inhibits the generation of virus-specific cytotoxic T cells when injected into mice infected with lymphocytic choriomeningitis virus. Thus G-TsF/TGF-beta 2 might contribute to the impairment of tumour immune surveillance. Some T cell clones may escape the immunosuppressive effects of TGF-beta: ovalbumin-specific T helper cell lines that showed different degrees of susceptibility to TGF-beta contained clones which had lost receptor(s) for TGF-beta.

Animals↗
PubMed1990

Sequence analysis of the promoter region of the glioblastoma derived T cell suppressor factor/transforming growth factor (TGF)-beta 2 gene reveals striking differences to the TGF-beta 1 and -beta 3 genes.

Human glioblastoma cells secrete a factor termed glioblastoma derived T cell suppressor factor (G-TsF) or transforming growth factor beta 2 (TGF-beta 2) which inhibits the response of T cells to mitogenic or antigenic stimulation. In the present study we isolated the promoter region of the G-TsF/TGF-beta 2 gene. The promoter region shares no homology to the promoter of the TGF-beta 1 or the 5' region of the TGF-beta 3 gene and harbours several familiar DNA motifs, including the cytokine-1 region, an octamer-like sequence, Sp1- and AP-2-like elements and a putative NF-kappa B site. In contrast to the TGF-beta 1 gene, the G-TsF/TGF-beta 2 gene contains three TATA-like sequences but lacks an AP-1 site. To understand the cell type specificity of expression of G-TsF/TGF-beta 2, the individual contribution of the DNA elements detected in the promoter has to be analysed in further studies.

Base Sequence↗
PubMed1990

Astrocytes and glioblastoma cells express novel octamer-DNA binding proteins distinct from the ubiquitous Oct-1 and B cell type Oct-2 proteins.

The 'octamer' sequence, ATGCAAAT or its complement ATTTGCAT, is a key element for the transcriptional regulation of immunoglobulin genes in B-lymphocytes as well as a number of housekeeping genes in all cell types. In lymphocytes, the octamer-binding protein Oct-2A and variants thereof are thought to contribute to the B-cell specific gene expression, while the ubiquitous protein Oct-1 seems to control general octamer site-dependent transcription. Various other genes, for example interleukin-1 and MHC class II genes, contain an octamer sequence in the promoter and are expressed in cells of both the immune and nervous systems. This prompted us to analyze the octamer-binding proteins in the latter cells. Using the electrophoretic mobility shift assay, at least six novel octamer binding proteins were detected in nuclear extracts of cultured mouse astrocytes. These proteins are differentially expressed in human glioblastoma and neuroblastoma cell lines. The nervous system-derived (N-Oct) proteins bound to the octamer DNA sequence in a manner which is indistinguishable from the Oct-1 and Oct-2A proteins. The relationship of the N-Oct proteins to Oct-1 and Oct-2A was analyzed by proteolytic clipping bandshift assays and by their reactivity towards antisera raised against recombinant Oct-1 and Oct-2A proteins. On the basis of these assays, all N-Oct-factors were found to be distinct from the ubiquitous Oct-1 and the lymphoid-specific Oct-2A proteins. In melanoma cells that contain the N-Oct-3 factor, a transfected lymphocyte-specific promoter was neither activated nor was it repressed upon contransfection with an Oct-2A expression vector. We therefore speculate that N-Oct-3 and other N-Oct factors have a specific role in gene expression in cells of the nervous system.

Animals↗