Antibodies to the ras gene product inhibit adenylate cyclase and accelerate progesterone-induced cell division in Xenopus laevis oocytes.

Microinjection of monoclonal antibodies (lines 238, 172, and 259) directed against the ras gene product, p21, into Xenopus laevis oocytes accelerated progesterone-induced germinal vesicle breakdown. Antibody 238 had the greatest effect on the acceleration of progesterone-induced oocyte maturation, and this effect was correlated with in vitro inhibition of adenylate cyclase (EC 4.6.

Analysis of viral and somatic activations of the cHa-ras gene.

The activation of the cHa-ras oncogene in the EJ/T24 bladder carcinoma cell line was compared with the activation of the same gene in the rat-derived Harvey murine sarcoma virus. The results indicate that, like the human oncogene, the Harvey murine sarcoma virus-borne ras gene owes its oncogenic capacity to point mutations in coding sequences rather than to the alteration in transcriptional control that occurred when the formerly cellular ras sequences were acquired by the virus. The viral gene retained its transforming ability when its transcription was removed from the influence of the retroviral long terminal repeat promoter and was placed under the regulation of the cHa-ras promoter.

Cloning and analysis of reverse transcript P160 genomes of Abelson murine leukemia virus.

Circular duplex reverse transcripts of the genome of a strain of Abelson murine leukemia virus that encodes a 160,000-molecular-weight protein were isolated, cleaved with HindIII restriction endonuclease, and cloned into the unique HindIII site of lambda phage Charon 21A. Recombinant phage clones, some of which were infectious in transfection assays, were found to contain a 789-base-pair region specific for Abelson murine leukemia virus; this region is not found in other strains of this virus. The extra sequence was localized by restriction endonuclease and electron microscopic heteroduplex analysis.

Mechanism of activation of a human oncogene.

The oncogene of the human EJ bladder carcinoma cell lines arose via alteration of a cellular proto-oncogene. Experiments are presented that localize the genetic lesion that led to activation of the oncogene. The lesion has no affect on levels of expression of the oncogene.

DNA methylation affecting the expression of murine leukemia proviruses.

The endogenous, vertically transmitted proviral DNAs of the ecotropic murine leukemia virus in AKR embryo fibroblasts were found to be hypermethylated relative to exogenous AKR murine leukemia virus proviral DNAs acquired by infection of the same cells. The hypermethylated state of the endogenous AKR murine leukemia virus proviruses in these cells correlated with the failure to express AKR murine leukemia virus and the lack of infectivity of cellular DNA. Induction of the endogenous AKR murine leukemia virus proviruses with the methylation antagonist 5-azacytidine suggested a causal connection between DNA methylation and provirus expression.

Human EJ bladder carcinoma oncogene is homologue of Harvey sarcoma virus ras gene.

Examination of homologies between retroviral oncogenes and transforming sequences defined by transfection reveals that the human bladder carcinoma (EJ) oncogene is homologous to the Harvey sarcoma virus oncogene (ras). Structural analysis limits the region of homology to a 3.0-kilobase SacI fragment of the EJ oncogene.

Adaptation of a retrovirus as a eucaryotic vector transmitting the herpes simplex virus thymidine kinase gene.

We investigated the feasibility of using retroviruses as vectors for transferring DNA sequences into animal cells. The thymidine kinase (tk) gene of herpes simplex virus was chosen as a convenient model. The internal BamHI fragments of a DNA clone of Moloney leukemia virus (MLV) were replaced with a purified BamHI DNA segment containing the tk gene.

Transfection of fibroblasts by cloned Abelson murine leukemia virus DNA and recovery of transmissible virus by recombination with helper virus.

A cloned, permuted DNA copy of the Abelson murine leukemia virus (A-MuLV) genome was capable of eliciting the morphological transformation of NIH/3T3 fibroblasts when applied to cells in a calcium phosphate precipitate. The efficiency of the process was extremely low, yielding approximately one transformant per microgram of DNA under conditions which give 10(4) transfectants per microgram of other DNAs (e.g.