RESUMEN
To test the hypothesis that the block of polyprotein precursor processing and particle formation in RSV-transformed mammalian cells is due to a low level of pr76gag expression, rat tumor cell lines with different amounts of precursor molecules were used. The wild-type forms of pr76gag have been expressed at a high level by use of SV40-based vector and thirty-two stable transfected cell clones were isolated. The gag protein expression was detected in the cell lysate by immunoblotting. Untransfected cells released no proteins that could be detected by immunoprecipitation with anti-RSV serum. Membrane-enclosed gag precursor-polyprotein molecules and infectious virus particles from different stably transfected clones have been found in the medium. Both immature and mature virions of type C morphology were directly detected by transmission electron microscopy. Surprisingly, virus-like particles of morphology similar to mature type C retroviruses were found enclosed within intracellular membranes in a stably transfected nonproducing clone.
Asunto(s)
Virus del Sarcoma Aviar/fisiología , Transformación Celular Viral , Regulación Viral de la Expresión Génica , Productos del Gen gag/biosíntesis , Genes gag , Virión/metabolismo , Replicación Viral , Animales , Virus del Sarcoma Aviar/genética , Virus del Sarcoma Aviar/aislamiento & purificación , Virus del Sarcoma Aviar/ultraestructura , Línea Celular Transformada , Productos del Gen gag/genética , Ratas , Sarcoma Experimental/patología , Transfección , Células Tumorales Cultivadas , Virión/ultraestructuraRESUMEN
In the newly established rat sarcoma cell line LSR-SF (SR) expression of pp60v-src was detected. Karyotype analyses revealed various chromosome aberrations during prolonged passaging of the tumor cells in vitro. Polyploidy was found to be a characteristic feature of the line studied. A large metacentric chromosome persistently present in the cells was accepted as a line marker.
Asunto(s)
Aberraciones Cromosómicas , Proteína Oncogénica pp60(v-src)/análisis , Sarcoma Experimental/genética , Animales , Virus del Sarcoma Aviar , Cariotipificación , Ratas , Células Tumorales CultivadasRESUMEN
The ability of molecular clones of human T-cell leukemia virus type I (HTLV-I) to direct the synthesis of infectious virions has not previously been demonstrated. An HTLV-I provirus originating from an adult T-cell leukemia patient was cloned into a plasmid vector and is designated pCS-HTLV. This molecular clone was shown to direct the synthesis of viral mRNA and proteins in transiently transfected cells; in addition, virus structural proteins were released into the culture medium. Viral proteins were assembled into virions that sedimented at a buoyant density characteristic of retrovirus particles and whose morphology was verified by electron microscopy. Virions concentrated from transiently transfected cell supernatants were incubated with primary cord blood lymphocytes or with transformed T-cell lines to establish that these particles were infectious. Expression of spliced, viral mRNAs in the T-cell cultures after both primary and secondary infections with cell-free virus revealed that pCS-HTLV encodes an infectious provirus.
Asunto(s)
Infecciones por HTLV-I/microbiología , Virus Linfotrópico T Tipo 1 Humano/crecimiento & desarrollo , Linfocitos T/microbiología , Secuencia de Bases , Clonación Molecular , Cartilla de ADN/química , Genes Virales , Virus Linfotrópico T Tipo 1 Humano/genética , Humanos , Técnicas In Vitro , Datos de Secuencia Molecular , ARN Viral/análisis , Transfección , Proteínas Estructurales Virales/genética , ViriónRESUMEN
The dynamics of expression of viral proteins gp51 and p24, virus particle production and mitotic activity of a highly productive bovine leukemia virus clone of the fetal lamb kidney (FLK) cell line were studied. The period of the highest protein production (20-44 h after incubation) was established by the indirect immunofluorescence method using specific monoclonal antibodies. It was followed by a complete formation of the cell monolayer and the most intensive period of the mitotic activity determined by the 3H-thymidine labeling method. After the active synthesis of viral protein, the formation of mature viral particles and their shedding in the intercellular spaces was established electron-microscopically and by the syncytia induction test. A similar comparative study was carried out with a BLV producing short-term lymphocyte culture (STLC).
Asunto(s)
Virus de la Leucemia Bovina/ultraestructura , Proteínas Virales/biosíntesis , Animales , Gatos , Bovinos , Línea Celular , Células Cultivadas , Replicación del ADN , ADN Viral/biosíntesis , Virus de la Leucemia Bovina/metabolismo , Mitosis , Ovinos , Proteínas del Envoltorio Viral/biosíntesis , Replicación ViralRESUMEN
R-type virus-like particles (VLP) in fibrosarcoma and myeloid tumour induced in hamsters with the myeloleukaemic virus of Graffi and in hamster embryonic fibroblasts infected with the lympholeukaemic virus Ly/Ya are described. The particles are found in the cysternae of the rough surface endoplasmic reticulum (RER). The VLP are classified as endogenous virus (EV) whose expression is determined by the initial infection with murine leukaemia virus (MLV).