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H Beug

Publications and source records attributed to H Beug.

At least 163 records · Page 9Linked to original sources
PubMed1982

Hormone-dependent terminal differentiation in vitro of chicken erythroleukemia cells transformed by ts mutants of avian erythroblastosis virus.

Chicken erythroblast cell strains and a cell line transformed by ts mutants of avian erythroblastosis virus (AEV) terminally differentiate when shifted to the nonpermissive temperature (42 degrees C). The differentiated cells resemble mature erythrocytes with respect to morphology and ultrastructure, expression of differentiation-specific cell-surface antigens, pattern of protein synthesis and hemoglobin content. Terminal differentiation is dependent on conditions favoring the differentiation of normal erythroid progenitor cells, including an erythropoietin-like factor. Colonies of ts AEV cells grown at 42 degrees C semisolid medium resemble erythrocyte colonies derived from normal erythroid progenitor cells. The colonies obtained were comparable in size or slightly larger than the late erythroid precursor (CFU-E) colonies. These results suggest that AEV-transformed cells are blocked at a stage of differentiation that is more advanced than that of the uninfected target cells. ts AEV cells are irreversibly committed to terminal differentiation within 20 to 30 hr after shift to 42 degrees C.

Alpharetrovirus↗
PubMed1982

Temperature-sensitive changes in the structure of globin chromatin in lines of red cell precursors transformed by ts-AEV.

Chicken bone marrow cells infected in vitro with a temperature-sensitive avian erythroblastosis virus fall to produce hemoglobin at 36 degrees C. When the product or products of the transforming gene (erb) are inactivated by a temperature shift to 42 degrees C in culture, several different cloned lines of cells infected with the temperature-sensitive avian erythroblastosis virus begin to make hemoglobin. This shift in phenotype correlates with an increase in hemoglobin mRNA specific to both adult and embryonic alpha and beta globin. The switch is accompanied by the acquisition of DNAase I-hypersensitive sites in one cell line (clone 2); however, a hypothetically more mature line (clone 3) has already acquired globin DNAase-hypersensitive sites but does not express hemoglobin until the temperature shift. Several (but not all) specific restriction sites associated with both the alpha and beta domains become unmethylated after the switch from 36 degrees C to 42 degrees C. The magnitude of these methylation switches is small compared with changes that occur in these genes during normal avian erythropoiesis. The results suggest that changes in chromosomal structure precede transcription and are not a consequence of transcription. Since (presumptive) precursor cloned lines can be established with some, but not all, of the structural properties of active globin chromatin, it is likely that many of these properties can be independently established and are not obligatorily related.

Alpharetrovirus↗
PubMed1982

Transformation of both erythroid and myeloid cells by E26, an avian leukemia virus that contains the myb gene.

E26 and avian myeloblastosis virus are replication-defective avian retroviruses that contain the myb oncogene and cause leukemia in chickens with short periods of latency. Animals infected with E26 develop erythroleukemia and also contain low numbers of transformed myeloid cells, while avian myeloblastosis virus induces a purely myeloid leukemia. In both cases the type of leukemia induced is independent of the subgroup of the helper virus used. E26-transformed erythroid and myeloid cells can each be propagated selectively from explanted leukemic cells with media supplemented with factors that promote the growth either of normal chicken erythroid precursors or of myeloid progenitor cells. E26 also induces the outgrowth of transformed cells from bone marrow cells infected in vitro. These cells are also either erythroid or myeloid, depending on the culture conditions employed. Most of the erythroid cells transformed by E26 are erythroblast-like, but a significant number are more mature, including erythrocyte-like cells as well as some cells that appear to be aberrant in differentiation. Both erythroid and myeloid E26-transformed cells produce infectious virus and express P135 E26, the putative (gag-myb-x) transforming protein of the virus. Thus E26 is a virus that is capable of generating factor-dependent transformed cells in two different hematopoietic lineages.

Animals↗
PubMed1982

Expression of a chicken lysozyme recombinant gene is regulated by progesterone and dexamethasone after microinjection into oviduct cells.

We transferred a chicken lysozyme gene recombinant by microinjection into primary cultures of chicken oviduct cells. The recombinant gene is a fusion between the lysozyme promoter, including 1.4 kb of upstream sequences, and the coding region of the gene for SV40 T antigen (plys-T). The expression of plys-T is stimulated by the steroid hormones progesterone and dexamethasone, but not by estradiol. The number of oviduct cells expressing coinjected or separately injected control genes is not increased by steroids. A deletion mutant lacking the lysozyme sequences between -161 and +15 does not express T antigen, indicating that transcription of plys-T starts within the lysozyme promoter region. By screening different cell types we found that microinjected plys-T is expressed in chicken oviduct cells but not in chicken macrophages or fibroblasts or in rat II fibroblasts.

Animals↗
PubMed1982

Expression of embryonic haemoglobin in tsAEV-transformed embryonic erythroid cells during temperature-induced differentiation.

Cells prepared from 1-day-old chick blastoderms were infected with a temperature-sensitive mutant of avian erythroblastosis virus (tsAEV). Clonal strains of transformed erythroblasts were isolated from the infected blastoderm cells. By shift to the nonpermissive temperature, these cells could be induced to differentiate into erythrocyte-like cells which expressed embryonic haemoglobins. Embryonic haemoglobins could not be detected in tsAEV-transformed erythroblasts from adult bone marrow when induced to differentiate under the same conditions. In contrast to normal primitive erythrocytes, tsAEV-infected embryonic erythroblasts differentiated in vitro expressed also adult haemoglobin. These results suggest an influence of the haematopoietic environment on the switch from embryonic to adult erythrocytes.

Alpharetrovirus↗
PubMed1981

Cell-surface glycoprotein synthesis during differentiation of chicken erythroblasts transformed by temperature-sensitive avian erythroblastosis virus.

Chicken erythroblasts transformed by a temperature-sensitive mutant of avian erythroblastosis virus (ts34 AEV) have a greatly increased haemoglobin content (Graf, T., N. Ade and H. Beug: Nature 275, 496-501 (1978)) if allowed to grow for 3-5 days at the non-permissive temperature (41 degrees C), instead of the permissive temperature (35 degrees C) of the virus. Cell-surface molecular changes during this differentiation were investigated by examining the glycoproteins synthesized by a ts34-transformed erythroblast cell line. These cells synthesized a greatly increased amount of a 94,000 molecular weight erythrocyte cell-surface glycoprotein beginning 2-6 h after a shift in growth temperature from 35 degrees to 41 degrees C, consistent with the proposal that such a shift releases these transformed cells from a differentiation block.

Alpharetrovirus↗
PubMed1980

Cell transformation by avian defective leukaemia viruses.

A comparative study of seven independently isolated defective leukaemia viruses has been carried out. Phenotypic analysis of the chicken bone marrow cells transformed in vitro allowed the separation of these seven viruses into three groups based on the differentiation phenotype of the transformed cell. Nucleic acid hybridization studies revealed that these seven viruses had acquired cellular sequences. Interestingly, these studies also showed that the viruses within the same biological grouping had acquired related sequences. This indicates that viruses that have acquired the same or similar cellular sequences have very similar oncogenic capabilities. Analysis of proteins expressed in cells transformed by these viruses demonstrated that the cellular sequences were usually inserted within the gene for the viral core proteins, gag. Therefore the cellular sequences are expressed as a gag-related fusion protein which has an amino-terminal region derived from the gag gene and a carboxy-terminal half derived from the cellular sequences. Two exceptions to this are discussed. The general conclusion from these studies is that defective leukaemia viruses transform cells by virtue of acquired host cellular sequences. The ability of these viruses to transform cells and the target cell specificity of the transformation depends on these cellular sequences.

Alpharetrovirus↗
PubMed1980

Target cell specificity of defective avian leukemia viruses: hematopoietic target cells for a given virus type can be infected but not transformed by strains of a different type.

Defective avian leukemia viruses of the avian erythroblastosis (AEV), avian myelocytomatosis (MC29), and avian myeloblastosis (AMV) type induce the proliferation of leukemic cells with properties of erythroblasts, macrophages, and myeloblasts, respectively. Their target cells can be separated and have properties of cells of the erythroid (AEV) and myeloid lineage (MC29 and AMV), respectively. In the present study we have shown that this target cell specificity is not due to the ability of the different strains to infect only certain types of hematopoietic cells. Instead, AEV was found to replicate in macrophages and to induce the expression of p75 AEV, its presumptive transforming protein. Likewise, MC29 was found to replicate in AEV-infected erythroblasts as well as in AMV-infected myeloblasts and to express the p110 MC29 protein in these cells. Superinfection with MC29 or AMV of ts34 AEV-infected erythroblasts did not impair their capacity to accumulate hemoglobin after shift to nonpermissive temperature. Our results support a model in which the transforming proteins of AEV, MC29, and MAV block the differentiation of their target cells by competitively inhibiting the action of a hypothetical homologous cellular differentiation protein synthesized in the corresponding target cells only.

Alpharetrovirus↗
PubMed1980

Mutant of avian erythroblastosis virus defective for erythroblast transformation: deletion in the erb portion of p75 suggests function of the protein in leukemogenesis.

Previous studies have shown that td359 AEV, a mutant of avian erythroblastosis virus (AEV), is unable to transform erythroblasts in vitro or in vivo but is capable of transforming fibroblasts in vitro and of causing sarcomas in chicks. In this paper we show that the mutant synthesizes a gag-gene related protein (delta p75) which is about 1000 daltons smaller than the protein, p75, induced by wild-type AEV. The mutant protein lacks 3 of the approximately 53 lysine-arginine tryptic peptides resolved in p75 and also contains an additional peptide. By cleavage of delta p75 with p15 protease and analysis of the fragments for size and peptide composition, the deletion in delta p75 could be located in the non-gag region of the molecule. In contrast, with p40 AEV, a second AEV-specific protein synthesized in in vitro translation experiments, there is no change in size of translation products obtained from td359 AEV RNA. Our data provide direct evidence that p75 is required for erythroblast transformation.

Alpharetrovirus↗