Patricia Kahn

v-erbA specifically suppresses transcription of the avian erythrocyte anion transporter (Band 3) gene

Previous work has established that the v-erbA oncogene inhibits the temperature-induced differentiation of chick erythroblasts transformed with temperature-sensitive oncogene mutants. Here we demonstrate that v-erbA in differentiating erythroblasts specifically arrests expression of the erythrocyte anion transporter (band 3) gene at the transcriptional level. The v-erbA-induced differentiation block can be overcome by inducing cells to differentiate at alkaline pH. Under these conditions, which possibly impair biological activity of v-erbA, the maturing cells now express the anion transporter gene at high levels. However, its transcription is specifically and rapidly suppressed if v-erbA activity is restored by culturing the cells at neutral pH. Similar but less pronounced inhibition of gene expression by v-erbA was observed for the delta-amino-levulinic acid synthase gene. Additional evidence obtained with an inhibitor of band 3 activity suggests that the v-erbA-induced inhibition of band 3 gene expression is at least partly responsible for the differentiation block caused by this oncogene.

v-erbA cooperates with sarcoma oncogenes in leukemic cell transformation

The v-erbB, v-src, v-fps, v-sea, and v-Ha-ras oncogenes induce avian erythroid progenitor cells to self-renew in an erythropoietin-independent manner. These transformed erythroblasts retain both their capacity to differentiate into erythrocytes and their requirement for complex growth media. However, previous studies showed that erythroblasts transformed by v-erbB plus v-erbA (which by itself is not oncogenic) are blocked in differentiation and grow in standard media. Here we show that the introduction of v-erbA into erythroblasts transformed with v-src, v-fps, v-sea, or v-Ha-ras likewise induces a fully transformed phenotype. It also reduces the capacity of ts sea- and ts erbB-transformed erythroblasts to differentiate terminally in an erythropoietin-dependent manner after a temperature shift. Cooperativity involving v-erbA also occurs in vivo since chicks infected with a retroviral construct encoding v-erbA and v-src develop both acute erythroblastosis and sarcomas.

Ts mutants of E26 leukemia virus allow transformed myeloblasts, but not erythroblasts or fibroblasts to differentiate at the nonpermissive temperature

The myb, ets-containing avian acute leukemia virus E26 transforms myeloblasts, erythroblasts, and fibroblasts in culture and causes a mixed erythroid/myeloid leukemia in chicks. We report the isolation and characterization of four E26 mutants that are temperature-sensitive (ts) for myeloblast transformation. At the permissive temperature, tsE26-transformed myeloid cells resemble macrophage precursors and proliferate rapidly, provided the growth medium contains chicken myelomonocytic growth factor (cMGF). When shifted to the nonpermissive temperature the cells stop growing and differentiate into macrophage-like cells, as determined by their expression of morphological, functional, and antigenic markers of normal macrophages. They also lose their responsiveness to cMGF and secrete a cMGF-like factor. Ts mutants of E26 retain their leukemogenicity and their ability to transform both erythroblasts and fibroblasts at the nonpermissive temperature, suggesting that the myb oncogene of E26 causes myeloblast transformation and that ets is responsible for erythroblast and fibroblast transformation.

EMBL data library

The EMBL Data Library was the first internationally supported central resource for nucleic acid sequence data. Working in close collaboration with its American counterpart, GenBank (1), the library prepares and makes available to the scientific community a comprehensive collection of the published nucleic acid sequences. This paper describes briefly the contents of the database, how it is available, and possible future enhancements of Data Library services.

Quail embryo fibroblasts transformed by four v-myc-containing virus isolates show enhanced proliferation but are non tumorigenic.

Quail embryo fibroblasts infected with any of the four natural avian myc gene‐containing virus strains (MC29, CMII, OK10 and MH2) or with the myb, ets‐containing E26 acute leukemia virus, were examined for their expression of several transformation‐associated parameters. All myc‐containing viruses, but not E26 or Rous sarcoma virus (used as a control) induced a dramatic stimulation of cell proliferation. In addition, the myc virus‐transformed cells exhibited prominent nucleoli, possibly as a consequence of their increased proliferation. Cells transformed by MC29, OK10, MH2 and E26 were capable of growing in semi‐solid medium and showed a loss of actin cables and, in most cases, of an ordered fibronectin distribution. All of the myc virus‐transformed fibroblasts, as well as the E26‐transformed cells, were unable to form tumors in nude mice, indicating that the myc gene (and the myb/ets genes) are not sufficient for the induction of a fully malignant phenotype in avian fibroblasts.

Transformation of mammalian fibroblasts and macrophages in vitro by a murine retrovirus encoding an avian v-myc oncogene

A murine retrovirus which expresses the avain v‐myc OK10 oncogene was constructed. The virus, denoted MMCV, readily transforms fibroblasts of established lines, such as mouse NIH/3T3 and rat 208F cells, to anchorage‐independent growth in agarose. The virus also transforms primary mouse cells: (i) virus‐infected macrophages are induced to form large colonies in semi‐solid media, and can easily be expanded into mass cultures; (ii) MMCV‐infected fibroblastic cells from mouse limb buds undergo morphological transformation and grow in semi‐solid medium. MMCV thus transforms both mouse fibroblastic cells and macrophages in vitro, in a fashion similar to the v‐myc‐containing avian viruses in chicken cells. The possibility of introducing a transforming myc gene into mammalian cells by virus infection provides a novel approach for studying the mechanism of myc transformation in cells from many lineages.

Oncogenes and growth control

I Growth Factors and Proto-Oncogenes in Development and Differentiation.- The Expression of Growth Factors and Growth Factor Receptors During Mouse Embryogenesis.- A Role for Proto-Oncogenes in Differentiation?.- Tissue-Specific Expression and Possible Functions of pp60c-src.- II Growth Factors, Receptors, and Related Oncogenes.- The Granulocyte-Macrophage Colony-Stimulating Factors.- Role of PDGF-Like Growth Factors in Autocrine Stimulation of Growth of Normal and Transformed Cells.- Transforming Growth Factor-?.- Transforming Growth Factor-?.- The Physiology of Epidermal Growth Factor.- Structural Relationships Between Growth Factor Precursors and Cell Surface Receptors.- Regulation of Cell Growth by the EGF Receptor.- Mutational Analysis of v-erbB Oncogene Function.- The c-fms Proto-Oncogene and the CSF-1 Receptor.- Activation of the c-src Gene.- Normal and Transforming N-Terminal Variants of c-abl.- Transformation by the v-abl Oncogene.- mos.- Structure and Function of the Human Interleukin-2 Receptor.- III Signal Transduction and ras Oncogenes.- Phosphorylation in Signal Transmission and Transformation.- Inositol Lipids and Cell Proliferation.- Protein Kinase C.- The Relevance of Protein Kinase C Activation, Glucose Transport, and ATP Generation in the Response of Haemopoietic Cells to Growth Factors.- Cytoplasmic pH and Free Ca2+ in the Action of Growth Factors.- Epidermal Growth-Factor Mediation of S6 Phosphorylation During the Mitogenic Response: A Novel S6 Kinase.- Role of G Proteins in Transmembrane Signaling: Possible Functional Homology with the ras Proteins.- The ras Gene Family.- RAS Genes and Growth Control in the Yeast Saccharomyces cerevisiae.- IV Gene Expression and Nuclear Oncogenes.- Regulation of Human Globin Gene Expression.- Regulation of Gene Expression by Steroid Hormones.- Enhancers as Control Elements for Tissue-Specific Transcription.- The Effect of DNA Methylation on DNA-Protein Interactions and on the Regulation of Gene Expression.- Trans-Acting Elements Encoded in Immediate Early Genes of DNA Tumor Viruses.- Transactivator Genes of HTLV-I, II, and III.- Involvement of Proto-Oncogenes in Growth Control: The Induction of c-fos and c-myc by Growth Factors.- Oncogenes and Interferons: Genetic Targets for Animal Cell Growth Factors.- Regulation of c-myc Expression in Normal and Transformed Mammalian Cells.- Properties of the myc and myb Gene Products.- The fos Oncogene and Transformation.- p53: Molecular Properties and Biological Activities.- V Malignant Transformation as a Multistep Process.- Oncogene Cooperativity in Stepwise Transformation of Rodent Embryo Fibroblasts by Polyoma Virus.- Role of the Middle T: pp60c-src Complex in Cellular Transformation by Polyoma Virus.- Oncogenes Cooperate, but How?.- Individual and Combined Effects of Viral Oncogenes in Hematopoietic Cells.- Multiple Factors Involved in B-Cell Tumorigenesis.- Molecular Events Associated with Tumor Initiation, Promotion, and Progression in Mouse Skin.- Amplification of Proto-Oncogenes and Tumor Progression.- Suppression of the Neoplastic Phenotype.- VI Oncogenesis in Transgenic Mice.- Oncogenesis in Transgenic Mice.

How do retroviral oncogenes induce transformation in avian erythroid cells

The v-erb B oncogene, as well as other oncogenes of the src-gene family transform immature erythroid cells from chick bone marrow in vivo and in vitro. The erb B-transformed erythroid cells differ from normal late erythroid precursors (CFU-E) in that they have acquired the capacity to undergo self-renewal as well as to differentiate terminally. They also do not require the normal erythroid differentiation hormone, erythro-poietin, for either process. Cooperation of v-erb B with a second oncogene, v-erb A, results in a differentiation arrest of the transformed cells, which now only use the self-renewal pathway. Studies with conditional and non-conditional mutants in both v-erb B and v-erb A will be presented to elucidate further how the transforming proteins encoded by these oncogenes, gp74erb B and gp75gag-erb A, affect the differentiation programme of the infected erythroid precursor with the outcome of hormone-independent leukaemic cells arrested at an early stage of erythroid differentiation.

Individual and Combined Effects of Viral Oncogenes in Hematopoietic Cells

Activation of proto-oncogenes is believed to play an important role in the development of human leukemia. For example, chronic myelocytic leukemia is characterized by the presence of a specific translocation which leads to the activation of the c-abl proto-oncogene (see Ben-Neriah and Baltimore, this Vol.). This activation leads to the selective outgrowth of an apparently normal pluripotent stem cell clone and granulocytic cells derived from it. Progeny from this stem cell clone become leukemic in a later step(s) which usually affects myeloid and occasionally also lymphoid cells. Similarly, Burkitt’s lymphoma is associated with a specific translocation which activates the c-myc gene, but this activation is not sufficient to induce the disease (see Klein, this Vol.). In both of these examples the nature of the secondary events required to generate the leukemic state is unclear.

Transformation Capacities of a Murine Retrovirus Encoding an Avian myc Oncogene

In trying to establish a system for the study of myc-induced in vitro transformation of mammalian cells, we have constructed a mammalian retrovirus encoding an avian myc oncogene. Its LTRs are derived from the Moloney Murine Leukemia Virus (MoMuLV) and the myc oncogene from the avian retrovirus OK10. A virus, denoted murine myc virus (MMCV), was recovered after cotransfecting NIH3T3 cells with MMCV and MoMuLV helper virus DNAs.