Glomerulosclerosis and renal cysts in mice transgenic for the early region of SV40

Considerable evidence indicates that genetic determinants play a major role in the pathogenesis of a variety of human and experimentally-induced renal diseases. There are, however, no firm data to indicate which genes or types of genes can induce or promote renal disease. The recently acquired ability to make specific alterations in the genetic background of an animal affords a unique opportunity to assess the effect(s) of a given gene on the structure and function of an organ of interest. Such modifications have been carried out in the creation of transgenic mice. We examined mice transgenic for the transforming gene encoding large T-antigen which is present in the early region of simian virus 40 (SV40). Renal lesions were present in most animals. While there was some heterogeneity in the type and severity of the renal lesions observed, a majority of the older mice displayed glomerulosclerosis and/or proliferative tubular lesions which in some were associated with multiple, large tubular cysts. The appearance of these lesions in mice transgenic for a transforming gene suggests that renal expression of a gene which controls cell proliferation may be associated with the development of glomerulosclerosis and renal cysts. These findings indicate a possible role for other transforming genes, or oncogenes, in the pathogenesis of glomerulosclerosis and cystic renal disease in humans and other animal models.

Entrance of SV40-transformed cells into G0 phase as revealed by a study using the G0-specific ts mutant tsJT60

The purpose of this study is to distinguish two possibilities that the transformed cells are blocked to enter a resting state (G0) and that they enter but are persistently stimulated to return to a growing cycle, using SV40-transformed tsJT60 cells as a model system. tsJT60 is a temperature-sensitive (ts) mutant of a Fischer rat cell line (3Y1), which is classified as a G0 mutant; i.e., the ts defect is not expressed within the growing cell cycle but is expressed only between G0 and S phases. We assumed that if the former possibility were the case, the transformed cells would not show any ts phenotype; and if the latter case, they might be ts. All SV40-transformed tsJT60 clones grew at 34 degrees C as well as SV40-transformed 3Y1 cells did at both temperatures. At 39.5 degrees C, some SV40-transformed tsJT60 clones grew (not ts) but others did not (ts) under conditions adequate for growth of untransformed cells. When clones that grew at 39.5 degrees C were cultured under conditions inadequate for growth of untransformed cells such as serum restriction or high cell density, they were ts for growth or even cytocidal at 39.5 degrees C. These results indicate that all clones of SV40-transformed tsJT60 cells are ts and the latter possibility is the case.

Demonstration of papillomavirus structural antigen in human urinary bladder neoplasia

Clear cells showing characteristic features of koilocytotic atypia were found in 41 (82%) of 50 paraffin sections of urinary bladder tumour. Papillomavirus common structural antigen was detected in seven (14%) of the samples using an avidin-biotin peroxidase staining technique. The results suggest a role for the human papillomavirus in the aetiology of urinary bladder neoplasia.

Analysis of middle tumor antigen and pp60c-src interactions in polyomavirus-transformed rat cells

The relative abundance of pp60c-src molecules associated with polyomavirus (Py) middle tumor antigen (MTAg) and the relative abundance of MTAg associated with pp60c-src in a variety of Py-transformed rat cells was determined by quantitative immunoblot analyses which detect pp60c-src or Py MTAg. The results demonstrate that approximately 5 to 10% of the total immunoprecipitable pp60c-src molecules in Py-transformed rat cells are stably associated with MTAg and have elevated protein kinase activities. In these same cells, it was found that approximately 10 to 15% of the detectable MTAg molecules are stably associated with pp60c-src. Other results presented in this report demonstrate that approximately 50 to 75% of the total MTAg-associated cellular tyrosine kinase activity potentially represents the enzymatic activity of pp60c-src, while the remaining 25 to 50% represents the activity of other cellular tyrosine kinases. Our results also show that most pp60c-src molecules associated with Py MTAg do not possess electrophoretic mobilities that are altered from those of pp60c-src molecules not associated with MTAg or pp60c-src molecules obtained from normal rodent cells.

Studies on the origin-specific DNA-binding domain of simian virus 40 large T antigen

The origin-specific DNA-binding domain of simian virus 40 large T antigen was analyzed, and its C-terminal boundary was found to be at or before amino acid 259. This does not include the zinc finger structural motif located at amino acids 302 to 320 (J. M. Berg, Science 232:485-486, 1986). Interestingly, N-terminal fragments of 266 and 272 amino acids and larger displayed dramatically reduced origin-binding activity. In addition, the specific DNA-binding properties of truncated proteins purified from both bacterial and mammalian sources were compared. Truncated T antigens from mammalian cells bound specific DNA fragments more efficiently than did their bacterial counterparts. These results implicate posttranslational modification with a role in regulating the DNA-binding activity of large T antigen.

Mouse mammary tumor virus (MMTV) particles in extraorbital lacrymal and urethral glands of endogenous MMTV-carrying mice

Expression of mouse mammary tumor virus (MMTV) antigens was observed in a wide variety of exocrine glands in adult mice by an immunoperoxidase method using rabbit antisera against gp52 and p27 of MMTV. Both exogenous and endogenous MMTV-carrying SHN, GRS/A, C3H and DDD-Mtv-2 mice expressed both antigens in the mammary, extraorbital lacrymal, urethral, parotid and submandibular glands of both sexes and prostate, seminal vesicle and epididymis but not in the Harder's, Zymbal's sublingual and uterine glands. Endogenous MMTV-free but exogenous MMTV-carrying BALB/cfC3H mice showed antigen expressions only in the mammary gland. BALB/c mice free from either endogenous or exogenous MMTV did not express viral antigens in any tissues examined. Electronmicroscopically, MMTV A and B particles were detected in the above mentioned MMTV antigen positive non-mammary organs in endogenous MMTV-carrying mice. The results suggested that the endogenously expressing Mtv genes might produce mature MMTV in these non-mammary glandular systems.

Levels of bovine papillomavirus RNA and protein expression correlate with variations in the tumorigenic phenotype of hamster cells

Three independent cell lines were established from primary cultures of LSH hamster embryo cells infected with bovine papillomavirus type 1 (BPV-1). Although these cell lines differed in their in vitro saturation densities, none was capable of colony formation in soft agar. Interestingly, two cell lines (BPV-HE1 and BPV-HE3) were tumorigenic in nude mice, syngeneic hamsters, and allogeneic hamsters, whereas BPV-HE2 was not. All three cell lines contained similar numbers of the BPV-1 genome (approximately 50 to 200 copies per cell). However, the nontumorigenic BPV-HE2 cell line contained very low levels of BPV-specific RNA and only small amounts of the BPV-1 E5 transforming protein. The efficiency and rate of tumor formation by BPV-HE1 and BPV-HE3 correlated directly with the apparent amount of viral E5 protein. This analysis suggests that there is a threshold level of BPV protein synthesis required for tumorigenicity, there is a continuum of tumorigenic phenotypes which may depend upon the level of BPV protein expression, and BPV-transformed hamster cells can withstand allogeneic transplantation.

Transcription of the cottontail rabbit papillomavirus early region and identification of two E6 polypeptides in COS-7 cells

Cottontail rabbit papillomavirus (CRPV) early proteins are present at very low levels in virus-induced tumors and cannot be detected by immunological methods. Furthermore, cells in culture are not readily transformed by the virus. To overcome these difficulties in identifying and characterizing the putative transforming protein(s) coded by the E6 open reading frame, the early cottontail rabbit papillomavirus region was expressed under the control of the late simian virus 40 promoter. Mapping of the transcripts in transiently transfected COS-7 cells indicated that transcription was initiated in the late region of simian virus 40. Two E6-coded polypeptides were identified, representing translation products initiated at the first and second AUG codons.

Use of viable-cell ELISA for detection of monoclonal antibodies recognizing tumor-associated antigens on bovine lymphosarcoma cells

An ELISA, using viable bovine lymphosarcoma cells, was developed to detect tumor-associated antigens (TAA) expressed on lymphosarcoma cells from cows with enzootic bovine leukosis (EBL). Monoclonal antibodies (MAB) against TAA were used. Using viable-cell ELISA, MAB reacted with tumor cells from 9 cows with EBL, but not with peripheral blood lymphocytes from 10 clinically normal cows. Titers of MAB against tumor cells from 1 cow with EBL were 2,048 (direct immunofluorescence assay), 8,192 (flow cytometry), 2,048 (fixed-cell ELISA), and 16,384 (viable-cell ELISA). Viable-cell ELISA was the most sensitive method for detection of TAA. Reactivities of 7 MAB to tumor cells from cows with EBL were compared between viable-cell ELISA and a complement-dependent antibody cytotoxicity test. Of 5 MAB with no cytotoxic activity against tumor cells, 3 were reactive against tumor cells from the same cow, as determined by viable-cell ELISA, with titers ranging from 128 to 2,048.

A short sequence in the COOH-terminus makes an adenovirus membrane glycoprotein a resident of the endoplasmic reticulum

The E19 protein of adenoviruses is a transmembrane protein that abrogates the intracellular transport of class I antigens by forming complexes with them in the ER. We show here that the E19 protein is retained in the ER even in the absence of class I antigens. To define the region conferring residency in the ER, we examined two mutant forms of the viral protein. A 5 amino acid extension of the 15-membered cytoplasmic tail of the protein reduces its interaction with class I antigens but does not change its intracellular distribution. Shortening the tail to 7 amino acids also diminishes the affinity for class I antigens; however, this mutant E19 protein becomes transported to the cell surface. Thus, we concluded that a small stretch of amino acids exposed on the cytoplasmic side of the ER membrane is responsible for the retention of the E19 protein in the ER.

Role of herpes simplex virus type-2 and human papilloma virus in penile cancers in Singapore

To detect the presence of Herpes Simplex Virus Type 2 (HSV-2) and Human Papilloma Virus (HPV), common structural antigens in penile cancers, 20 squamous cell carcinomas were studied by immunohistochemical methods. All specimens were from Singaporeans ranging in age from 44 to 69 years. None of the specimens contained HSV-2 and HPV common structural antigens. The reasons for the absence of HPV common antigen were discussed. The significance of the association of HPV with penile cancers is uncertain. The role of HPV in the carcinogenesis of penile cancer is far from clear. Further studies need to be done and other possible causes have to be explored.

[Determination of the early antigens induced by herpes simplex virus in human tumors by a radioimmunological binding method]

It is very difficult to produce specific antibody to individual antigens comprising the multicomponent antigenic system of a cell. It is particularly true of the antigens present in the cell in small amounts and characterized by low immunogenic potency, among them early antigens of herpes simplex virus (HSV). To overcome these difficulties the authors propose a method of preparation of a specific serum using specific immune complexes as immunogens. The use of the radioimmune binding method and a new specific serum to early HSV antigen has proved that HSV could be associated not only with cervical carcinoma, as believed by many research workers, but also with tumors of other localization, in particular, lung carcinoma and malignant melanomas.

Immunoelectron microscopic localization of mammary tumor virus (MTV) antigens in normal and cancerous mammary glands of mice

Peroxidase-labeled Fab' fragments of rabbit antisera against gp52 (major envelope protein) and A-particles of mammary tumor virus (MTV) were prepared and used for investigation by immunoelectron microscopy of the replication cycle of MTV-specific envelope and core antigens in normal and malignant mammary gland cells of female mice. The specificity of the antisera was proven by absorption tests and lack of reactivity to MTV-free mammary tissues. Periodate-lysine-paraformaldehyde (PLP) fixation sufficiently preserved the antigenicity of gp52, while Zamboni's fixative was useful to preserve the core antigen. Saponin pretreatment was necessary to reveal the intracellular antigen of A particles but had no influence on gp52. In addition to its presence at the envelope of D particles, gp52 was clearly associated with the biomembrane system, including the nuclear membrane, endoplasmic reticulum, Golgi apparatus and plasma membrane independent of the presence of virus particles. In mammary tumors, a significant level of gp52 antigen was often expressed on the entire cell surface membrane. In contrast, it was localized only to the apical plasma membrane in normal mammary gland cells. A particle antigens were confined to the intracytoplasmic A particles, usually visible as clusters, and to the inner part of B particles. These ultrastructural findings support the available biochemical data on the morphogenesis of MTV particles.

Protein disulfide crosslinking stabilizes a polyoma large T antigen-host protein complex on the nuclear matrix

We have investigated the effects of intermolecular disulfide crosslinking and temperature-dependent insolubilization of nuclear proteins in vitro on the association of the polyoma large T antigen with the nuclear matrix in polyomavirus-infected mouse 3T6 cells. Nuclear matrices, prepared from polyomavirus-infected 3T6 cells by sequential extraction of isolated nuclei with 1% Triton X-100 (Triton wash), DNase I, and 2 M NaCl (high salt extract) at 4 degrees C, represented 18% of total nuclear protein. Incubation of nuclei with 1 mM sodium tetrathionate (NaTT) to induce disulfide crosslinks or at 37 degrees C to induce temperature-dependent insolubilization prior to extraction, transferred an additional 9-18% of the nuclear protein from the high salt extract to the nuclear matrix. This additional protein represented primarily an increased recovery of the same nuclear protein subset present in nuclear matrices prepared from untreated nuclei. Major constituents of chromatin including histones, hnRNP core proteins, and 98% of nuclear DNA were removed in the high salt extract following either incubation. Polyoma large T antigen was quantified in subcellular fractions by immunoblotting with rat anti-T ascites. Approximately 60-70% of the T antigen was retained in nuclei isolated in isotonic sucrose buffer at pH 7.2. Most (greater than 95%) of the T antigen retained in untreated nuclei was extracted by DNase-high salt treatment. Incubation at 37 degrees C or with NaTT transferred most (greater than 95%) of the T antigen to the nuclear matrix. T antigen solubilized from NaTT-treated matrices with 1% SDS sedimented on sucrose gradients as a large (50-S) complex. These complexes, isolated by immunoprecipitation with anti-T sera, were dissociated by reduction with 2-mercaptoethanol, and SDS-PAGE analysis revealed that T antigen was crosslinked in stoichiometric amounts to several host proteins: 150, 129, 72, and 70 kDa. These host proteins were not present in anti-T immunoprecipitates of solubilized nuclear matrices prepared from iodoacetamide-treated cells. Our results suggest that the majority of polyomavirus large T antigen in infected cells is localized to a specific subnuclear domain which is distinct from the bulk chromatin and is closely associated with the nuclear matrix.

The role of individual cysteine residues in the structure and function of the v-sis gene product

The v-sis oncogene encodes a platelet-derived growth factor (PDGF)-related product whose transforming activity is mediated by its functional interaction with the PDGF receptor. PDGF, as well as processed forms of the v-sis gene product, is a disulfide-linked dimer with eight conserved cysteine residues in the minimum region necessary for biologic activity. Site-directed mutagenesis of the v-sis gene revealed that each conserved cysteine residue was required directly or indirectly for disulfide-linked dimer formation. However, substitution of serine for cysteine codons at any of four positions had no detrimental effect on transforming activity of the encoded v-sis protein. These results establish that interchain disulfide bonds are not essential in order for this protein to act as a functional ligand for the PDGF receptor. The remaining four substitutions of serine for cysteine each inactivated transforming function of the molecule. In each case this was associated with loss of a conformation shown to involve intramolecular disulfide bonds. These studies provide insight into the role of individual cysteine residues in determining the structure of the sis/PDGF molecule critical for biological activity.

Cell fusion by nasopharyngeal carcinoma-derived Epstein-Barr virus

Cell fusion experiments using Epstein-Barr virus (EBV) obtained from nasopharyngeal carcinoma (NPC) hybrid cells (NPC-KT) were carried out to examine whether human adenoid epithelial cells (Ad-AH) could be fused with lymphoblastoid cells (BJAB, Raji, and A2L) superinfected or infected by EBV, and if Ad-AH nuclei of the fused cells could express EBV-associated nuclear antigen. The presence of NPC EBV could induce EBV early antigen in all three lymphoblastoid cell lines. By autoradiography, we found that NPC EBV could induce cell fusion between Ad-AH cells and tritiated thymidine-labeled lymphoblastoid cells. In addition, we found that Ad-AH nuclei of the fused cells expressed EBV-associated nuclear antigen four days after NPC EBV-mediated cell fusion of Ad-AH cells with lymphoblastoid cells.

BK virus in cell culture: infectivity quantitation and sequential expression of antigens detected by immunoperoxidase staining

We applied an indirect immunoperoxidase staining method for the detection of BK virus (BKV) antigens in Vero cells. By immunoperoxidase staining of sequential samples, expression of BKV T- and structural antigens was first detectable 72 h postinfection (pi). The initial low number of antigen positive cells was slowly increasing until 6 d pi. Thereafter, a steady progression was observed until total cytopathogenic effect 30 d pi. Viral hemagglutinins were detected 11 d pi in both the culture medium and in the cell lysate. Passage of the preparations into fresh Vero cells and immunoperoxidase detection demonstrated the presence of infectious virions in both the cell lysates and the medium from 2 d pi. The number of infectious particles in both media and cell lysates correlated to the number of IP stained cells in the sequential staining. We suggest that this type of assay might be used to examine the effects, in vitro, of interferons and other virostatic drugs of BKV and other viruses.

Variations in polyoma virus genotype in relation to tumor induction in mice. Characterization of wild type strains with widely differing tumor profiles

The authors have explored the effects of variations in mouse polyoma virus genotype on patterns of tumor formation in the mouse. Four "wild type" virus strains were surveyed. Two were highly oncogenic, inducing multiple tumors of epithelial and mesenchymal origin, at high frequency and with short latency. The other two strains were weakly oncogenic, inducing fewer tumors, solely of mesenchymal origin, and after a long latency. These sharply contrasting tumor profiles were reproduced with virus stocks derived from molecularly cloned viral genomes. Though vastly different in their oncogenic properties, these cloned viruses proved equally effective in transforming established rat fibroblasts in culture and showed the same patterns of tumor antigen expression in cultured mouse cells. Complexes of polyoma middle T antigen and pp60c-src were demonstrated in extracts of epithelial tumors induced by a highly oncogenic virus strain. It is concluded that polyoma viral genetic determinants for tumor induction in the mouse are more complex than those previously defined by the use of cell transformation systems.

Owl monkey astrocytoma cells in culture spontaneously produce infectious JC virus which demonstrates altered biological properties

A tumor cell suspension of an explanted JC virus (JCV)-induced owl monkey glioblastoma was inoculated intracranially into four recipient juvenile owl monkeys. Twenty-eight months following inoculation one owl monkey developed a glioblastoma, which was explanted into tissue culture. DNA from both the tumor tissue and tumor cells in culture hybridized to a JCV DNA probe by Southern analysis, indicating that free, as well as integrated, viral DNA may be present. At the time of the second culture passage, viral JCV DNA was extracted from these cells and cloned into a plasmid vector. Nucleotide sequencing of the regulatory region of the cloned DNA demonstrated homology with the prototype Mad-1 strain of JCV and revealed a 19-base-pair deletion in the second 98-base-pair tandem repeat that eliminated a second TATA box. This deletion is characteristic of the Mad-4 strain of JCV, which is highly neurooncogenic. By the third culture passage, 100% of the cells were T-antigen positive. Approximately one-third of the cells in culture hybridized to a biotinylated JCV DNA probe when in situ hybridization was used, a technique that only detects high-copy-number of replicating viral sequences. By the culture passage 5 and continuing through culture passage 14, viable JC virions could be recovered. The T protein synthesized by this virus, now termed JCV-586, differed from both the Mad-1 and Mad-4 strains in that it formed a stable complex with the cellular p53 protein in the tumor cells. Also, the JCV-586 T protein reacted to several monoclonal antibodies made to the simian virus 40 T protein that were not recognized by either the Mad-1 or Mad-4 strains.

Fate and expression of simian virus 40 DNA after introduction into murine cells under nonselective conditions

When SV40 infects mouse cells, it does not replicate but instead causes neoplastic transformation of a small percentage of the cells. It is unknown, however, what happens to the virus in those cells that do not become transformed. We introduced SV40 into mouse cells by nonselective means, either by cotransfection of SV40 DNA with a selectable marker or by random cloning of SV40-infected cells. We analyzed the fate of viral DNA sequences, expression of T antigens, and transformation properties of these cells. We found that, upon infection, viral DNA integration occurs at a frequency that is at least 10-fold higher than the frequency of transformation. The majority of these cells are not transformed due to lack of expression of T antigen. One cell line which expresses a truncated T antigen is not transformed. We have mapped the viral sequences in the genome of these cells and find that integration in the large T intron is probably responsible for the defect. Lack of transformation can therefore be attributed to both cellular and viral factors, namely, introduction of viral DNA into cells that are resistant to transformation or integration of viral DNA in such a way that T antigen expression is prohibited.

Biochemical properties associated with the immortalizing domain of the large T protein of polyoma virus

A fragment of polyoma virus DNA lacking the carboxy-terminal part of the large T antigen coding region is sufficient to express the functions of the entire gene in cell transformation. Two cell lines expressing this truncated DNA were studied, one of them producing a large T-related protein of the expected size (37 kDa) and the other one, a shorter product (34 kDa). Both proteins were phosphorylated and localized in the nucleus, but devoid of ATPase and nucleotide binding activities. As the complete protein, the larger product, but not the shorter variant, exhibited sequence-specific DNA binding properties. These results indicate that ATPase and nucleotide-binding activities are not required for immortalization, and suggest that recognition of specific DNA sequences may be dispensable.

Experimental studies on Marek's disease in Japanese quail (Coturnix coturnix japonica)

Day-old quails experimentally infected with Marek's disease (MD) virus of quail origin developed lymphoid tumors. The severity of the disease increased considerably with serial passage. Tumor transplants could be made with cells derived from gross tumors in skeletal muscles, spleen cells, and blood from MD-affected quails. After five to six serial transplants, the tumor could not be transplanted further. Marek's disease tumor-associated surface antigen (MATSA) was demonstrated in lymphoid cells of spleen and peripheral blood lymphocytes of MD-affected quails. The MATSA of quail differed from the MATSA of chicken. Chickens were susceptible to MD virus isolated and propagated in quails.

Synthetic antigens as immunogens: Part II: Antibodies to synthetic T antigen

Antibody to the carbohydrate moiety of T antigen was developed. The synthetic antigen (Gal beta 1----3 GalNAc alpha 1----OC6H4N = N-BSA) was prepared by coupling the diazonium salt of the disaccharide derivative Gal beta 1----3 GalNAc alpha 1----OC6H4NH2 (o) with bovine serum albumin. Specificity of the antibody produced was examined with structurally related synthetic saccharides using the enzyme immunoassay technique. The presence of a glycosyl group at 0-6 of either the Gal or the GalNAc residue of the disaccharide Gal beta 1----3 GalNAc did not prevent binding of the antisera to the saccharide moiety. However, the antisera did not bind either the trisaccharide moiety NeuAc2----3 Gal beta 1----3 GalNAc alpha 1----OC6H4NO2 (o) or GlcNAc beta 1----3 Gal beta 1----3 GalNAc alpha OBn. These observations indicate that antibody approach to the antigen is to the 0-3 side of the terminal galactose in the disaccharide Gal beta 1----3 GalNAc. We have also observed that the antibody prefers Gal beta 1----3 GalNAc alpha 1----to Gal beta 1----3 GalNAc beta 1----disaccharide derivatives in its binding capacity. The antibody was found to bind natural T antigen present on neuraminidase-treated red blood cells and, by immunohistochemical analysis, it was found to bind to naturally occurring T antigen on breast tumor cells.

Oncogenesis of the lens in transgenic mice

Neoplastic tumors of the ocular lens of vertebrates do not naturally occur. Transgenic mice carrying a hybrid gene comprising the murine alpha A-crystallin promoter (-366 to +46) fused to the coding sequence of the SV40 T antigens developed lens tumors, which obliterated the eye cavity and even invaded neighboring tissue, thus establishing that the lens is not refractive to oncogenesis. Large-T antigen was detected early in lens development; it elicited morphological changes and specifically interfered with differentiation of lens fiber cells. Both alpha- and beta-crystallins persisted in many of the lens tumor cells, while gamma-crystallin was selectively reduced. Accessibility, characteristic morphology, and defined protein markers make this transparent epithelial eye tissue a potentially useful system for testing tumorigenicity of oncogenes and for studying malignant transformation from its inception until death of the animal.

Expression of the 6C3 antigen on murine hematopoietic neoplasms. Association with expression of abl, ras, fes, src, erbB, and Cas NS-1 oncogenes but not with myc

The monoclonal antibody 6C3 was used to test a wide variety of murine hematopoietic neoplasms for cell surface expression of a 160 kD glycoprotein (gp160(6C3)) previously shown to be expressed by neoplastic pre-B and some B lymphocytes transformed by Abelson murine leukemia virus (A-MuLV). This antigen was expressed on many pre-B and B cell lymphomas, but not on A-MuLV-transformed fibroblasts, T cell lymphomas, or myelomonocytic leukemias, gp160(6C3) was expressed by most early B-lineage spontaneous tumors, and early B tumors induced by replication-defective MuLV-containing oncogenes the products of which are associated with the cytoplasmic aspect of the plasma membrane, i.e., fes, abl, H-ras, bas, src, erbB, and Cas NS-1. By comparison, none of the early B lineage lymphomas induced by the "nuclear" oncogene avian v-myc MuLV, or arising in mice transgenic for a murine c-myc gene, or later B cell lineage stages bearing translocations of the c-myc locus expressed this antigen.