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S Spiegelman

Publications and source records attributed to S Spiegelman.

At least 19 recordsLinked to original sources
PubMed1979

RNA replication: required intermediates and the dissociation of template, product, and Q beta replicase.

Replication complexes containing only one molecule of Q beta replicase and one strand of midivariant RNA (MDV-1 RNA) template were prepared by incubating the replicase with an excess of MDV-1 (-) RNA. In the presence of excess minus strands, these monoenzyme replication complexes were shown to synthesize essentially pure MDV-1 (+) RNA in both the first and second cycles of replication. When an equivalent concentration of mutant MDV-1 (-) RNA was added to this reaction before completion of the first cycle of replication, only wild-type MDV-1 (+) RNA was produced in the first cycle, but both mutant and wild-type MDV-1 (+) RNA were produced in the second cycle of replication. These results demonstrate that a monoenzyme complex is competent to synthesize RNA and, therefore, that a multienzyme replication complex is not a necessary intermediate of replication. The data also imply that after the completion of chain elongation, the product strand is released from the replication complex and that the template and the replicase then dissociate.

Coliphages↗
PubMed1979

Human breast carcinoma antigen is immunologically related to the polypeptide of the group-specific glycoprotein of mouse mammary tumor virus.

We have shown [Mesa-Tejada, R., Keydar, I., Ramanarayanan, M., Ohno, T., Fenoglio, C. & Spiegelman, S. (1978) Proc. Natl. Acad. Sci. USA 75, 1529--1533] that an antigen immunologically related to gp52, a 52,000-dalton glycoprotein of the mouse mammary tumor virus, can be identified in sections of human breast cancer by means of an indirect immunoperoxidase technique. The specificity of the reaction was established by absorption experiments which revealed that only purified gp52, or material containing it, served to eliminate the IgG molecules responsible for the immunohistochemical reaction in the human breast tumors. We show here that the cross-reactivity between the human and murine tumor antigens is due to the polypeptide rather than the polysaccharide components of gp.52. Sugar-free gp52 prepared by deglycosylation with a mixture of glycosidases was as fully effective as the intact gp52 in removing from anti-MMTV the IgG responsible for the reaction with the human tumor antigen. In contrast, the isolated polysaccharide of gp52 was unable to exert blocking activity.

Animals↗
PubMed1978

Sodium pyrophosphate inhibition of RNA.DNA hybrid degradation by reverse transcriptase.

Sodium pyrophosphate inhibits synthesis of anticomplementary DNA during a reverse transcriptase (RNA-directed DNA nucleotidyltransferase, EC 2.7.7.7) catalyzed reaction. In the presence of pyrophosphate, the complementary DNA remains stably complexed to the RNA template. In the absence of pyrophosphate, the DNA. RNA hybrid template is degraded and anticomplementary DNA is synthesized. High concentrations of additives containing phosphodiester bonds appear to inhibit the ribonuclease H activity (hybrid nuclease, EC 3.1.4.34) of the reverse transcriptase, therby preventing formation of RNA primers necessary for the synthesis of anticomplementary DNA.

Diphosphates↗
PubMed1978

Detection of viral proteins in mouse mammary tumors by immunoperoxidase staining of paraffin sections.

An indirect immunoperoxidase method is described, which can readily detect viral antigens in paraffin sections of primary, transplanted, and metastatic mammary tumors of mice. In addition to having the obvious advantage of not being limited to fresh specimens, immunoperoxidase staining of paraffin sections proved to be superior in many respects when compared with immunofluorescence and frozen sections. Immunoperoxidase staining of paraffin sections is permanent and provides the kind of histological detail required for precise cytological identification and localization with light microscopy. All of 25 tumors and 4 metastatic lesions showed evidence of glycoprotein gp52 as well as other mouse mammary tumor viral antigens. The pattern and intensity of the stain were related to the degree of histologic differentiation of the tumor. Wide variations in expression of viral antigens by individual malignant cells were observed within the same tumor.

Animals↗
PubMed1978

Detection in human breast carcinomas of an antigen immunologically related to a group-specific antigen of mouse mammary tumor virus.

An antigen immunologically related to a group-specific antigen (gp52, a 52,000-dalton glycoprotein) of the mouse mammary tumor virus has been identified in paraffin sections of human breast cancers by means of the indirect immunoperoxidase technique. The specificity of the reaction with antibody against mouse mammary tumor virus was examined by absorption of the IgG with the following: (a) purified gp52; (b) a number of virus preparations (mouse mammary tumor virus, Rauscher leukemia virus, simian sarcoma virus, baboon endogenous virus, and Mason-Pfizer monkey virus); (c) normal plasma, leukocytes, breast tissue, milk, actin, collagen, and hyaluronic acid, all of human origin; (d) sheep erythrocytes and mucin. Only mouse mammary tumor virus (from C(3)H or Paris RIII strains and grown in either murine or feline cells) and purified gp52 eliminated the immunohistochemical reaction in the human breast tumors. Positive reactions were seen in 51 of 131 (39%) breast carcinomas of various histologic types, a minimal estimate in view of the limited number of sections from each tumor that could be examined. Negative reactions were obtained in all 119 benign breast lesions (cystic disease, fibroadenoma, papilloma, gynecomastia) and in all 18 normal breast tissues. With one exception, 99 carcinomas from 13 organs other than breast and 8 cystosarcomas were all negative.

Adenocarcinoma↗
PubMed1978

Contrasting characteristics of Marek's disease herpesvirus isolated from chickens with and without avian leukosis virus infection.

Marek's disease herpesvirus (MDHV) isolated from chickens free of naturally occurring avian leukosis virus (ALV) infection produced characteristic foci in both chicken embryo fibroblast (CEF) and chicken kidney cell (CKC) cultures. MDHV-A, which was extracted from the feather follicle epithelium of chickens naturally infected with ALV, did not induce cytologic changes in CEF cultures, but did cause focus formation in CK cultures. ALV was detected in MDHV-A, but not in MDHV preparations. MDHV-A (reconstructed in vivo) and MDHV were further distinguished from one another by inoculation of ALV-free LSI-SPF chickens. MDHV-A elicited a high incidence of early mortality which was not accompanied by the gross tumor spectrum characteristic of Marek's disease, although extensive histologic lesions were present. The differences between MDHV and MDHV-A were not as striking in another line of ALV-free chickens (SPAFAS). By contrast, among conventional chickens with naturally occurring ALV infection, neither MDHV-A nor MDHV caused appreciable early mortality although both were highly oncogenic (gross tumor development). These observations demonstrate that the presence of an oncornavirus (ALV), detected by radioimmune but not complement fixation assays, can influence the in vitro and in vivo characteristics of an oncogenic herpesvirus (MDHV). The observations recorded here resolve some of the inconsistencies reported in the literature. Thus, the apparent failure by some to find interactions between MDHV and oncornaviruses can be ascribed to the comparatively limited sensitivity of the complement fixation assay used to detect oncornaviruses (ALV). We have shown that the presence of oncornavirus detectable by radioimmune assay, but not by complement fixation, can influence the in vitro and in vivo responses of an oncogenic herpesvirus (MDHV). Our observations relating to viral interaction do not imply that MDHV required the presence of ALV to produce disease.

Animals↗
PubMed1978

Immunohistochemical detection of a cross-reacting virus antigen in mouse mammary tumors and human breast carcinomas.

An indirect immunoperoxidase method was first used to localize mouse mammary tumor virus (MMTV) antigens in paraffin sections of mammary tumors of Paris RIII and CD8F1 mice. By using the same method, an antigen with cross-reactivity to a group-specific antigen (gp52, a 52,000 dalton glycoprotein) of MMTV was detected in paraffin sections of human breast carcinomas. The specificity of this reaction with antibody against MMTV was examined by absorption of the IgG with: a) purified gp52; b) several relevant and irrelevant viral preparations; c) normal human plasma, leukocytes, breast tissue, milk, actin, collagen, and hyaluronic acid; d) sheep erythrocytes, bovine mucin and fetal calf serum. Only MMTV and prufied gp52 eliminated the immunohistochemical reaction in human breast tumors. Positive reactions were seen in 73 of 191 (38%) breast carcinomas of various histopathologic types, while negative reactions were obtained in all 137 normal and benign cases tested. A positive reaction of uncertain specificity was observed in foci of apocrine metaplasia. With one exception, 99 carcinomas from 13 organs other than breast and eight cystosarcomas were negative.

Adenocarcinoma↗
PubMed1977

Plasma levels of a viral protein as a diagnostic signal for the presence of mammary tumor: the effect of tumor removal.

We have previously shown (1, 2) that mice with mammary tumors can always be identified by their very high plasma levels of gp52, a 52,000 mol wt glycoprotein of the mouse mammary tumor virus (MMTV). The present investigation demostrates that the tumor is the principal source of the plasma gp52 since surgical excision is invariably followed in the first 9 days by a sharp decreasing (10-100-fold) of the gp52 levels. Control animals in which the tumors were left in place by a "sham" surgical procedure maintained their high level of gp52, which continued to increase as the disease progressed. The behavior of the gp52 after surgical removal suggests that gp52 plasma concentrations are diagnostically and prognostically informative, as indicated by the following finding: (a) All tumor recurrences were correctly diagnosed by increases in gp52 levels, and some were detected 4-7 days before they were found by palpation. (b) Tumor regrowths were accompanied by continued increases in plasma gp52 concentrations at rates that usually matched the speed of tumor development. (c) The only animals that remained tumor free at the termination of the experiment were those that maintained their gp52 levels at or below 15 ng/ml. (d) The probability of a tumor-free animal relapsing within 2 wk is much higher if its gp52 level is above the mean. (e) More remarkably, the plasma levels of gp52 at the time of surgery are superior to the size of the tumors removed as prognostic indicators of eventual surgical "cures". The availability of a specific and sensitive systemic measure of disease status should augment the usefulness of the murine mammary tumor model by catalyzing a more rapid acquisition of information on the therapeutic effectiveness of the new and varied drug combinations being tested for adjuvant chemotherapy.

Animals↗
PubMed1977

Purification and characterization of the DNA polymerase of human breast cancer particles.

Previous studies have identified human breast tumor particles possessing many of the features characteristic of RNA tumor viruses. In addition to the expected size (600 S) and density (1.16 g/ml) these include possession of an outer membrane and an inner one surrounding a "core" containing a DNA polymerase and a large-molecular-weight (70S) RNA possessing detectable homology to the RNAs of the mouse mammary tumor virus (MMTV) and of the Mason-Pfizer monkey virus (MPMV). We report here the purification and characterization of the DNA polymerase from the human breast cancer particles. Its key properties are very similar to those ofthe RNA-dependent DNA nucleotidyltransferase (reverse transcriptase) found in MMTV and MPMV. Thus like these viral enzymes, the purified human breast cancer DNA polymerase exhibits the following three features that together distinguish the known viral reverse transcriptases from normal cellular DNA polymerases: (i) a strong preference for oligo(dT)-poly(rA) over oligo(dT)-poly(dA) as a template for the synthesis of poly(dT); (ii) the acceptance of the highly specific oligo(dG)-poly(rCm) as a template for the formation of poly(dG); (iii) the ability to use a viral RNA (AMV) as a template to fashion a faithful DNA complementary copy; and (iv) its preference for Mg++ over Mn++. In summary, the data described here on the enzyme of the human breast cancer particles add further evidence of similarities to the viral agents associated with the corresponding malignancies in the mouse and monkey models. To date, an enzyme with these properties has not been detected in normal breast tissues or in benign tumors of the breast.

Breast Neoplasms↗
PubMed1977

Antigenic relatedness of the DNA polymerase of human breast cancer particles to the enzyme of the Mason-Pfizer monkey virus.

We have previously reported [(Ohno, T., Sweet, R.W., Hu, R., DeJak, D. & Spiegelman, S. (1977) Proc. Natl. Acad. Sci. USA 74, 764-768)] on the purification and characterization of the DNA polymerase from human breast cancer particles. Its preference for certain synthetic templates and its ability to use a viral RNA to fashion a faithful DNA transcript identify it as a reverse transcriptase similar to that found in the mouse mammary tumor virus and in the Mason-Pfizer monkey virus (MPMV). We report here that the human breast cancer enzyme crossreacts immunologically with the reverse transcriptase of MPMV. The crossreactivity was shown both by inhibition of enzyme activity and by complex formation between purified enzyme and isolated IgG against MPMV polymerase. No such interactions were observed with other oncornavirus reverse transcriptases of avian, murine, feline, or simian origin. Further, the IgG failed to neutralize the reverse transcriptases from human mesenchymal neoplasias (leukemias and lymphomas) or the activities of normal cellular DNA polymerases (alpha, beta, gamma).

Animals↗
PubMed1977

Synthesis of full-length DNA copies of avian myeloblastosis virus RNA in high yields.

The synthesis of full-length complementary DNA copies of avian myeloblastosis virus RNA is described. The cDNA is estimated by electrophoresis in agarose-methylmercury gels to have a molecular weight of 2.6 X 10(6), equivalent in size to that of the RNA template. Most (60-70%) of the reaction product is the full-length material and yields correspond to 60-70% of the input RNA.

Avian Leukosis Virus↗
PubMed1977

An improved procedure for purifying RNA tumor viruses from malignant tissue.

A convenient method for purifying RNA tumor viruses is described. Viruses banded in isopycnic gradients are contaminated with membranes that can be removed by velocity sedimentation in glycerol gradients. On sodium dodecyl sulfate (SDS) gel electrophoresis, the particles purified by these procedures from mouse mammary tumor tissue show protein profiles typical of those observed with virus purified from milk.

Animals↗
PubMed1976

Reverse transcriptase in leukocytes of leukemic patients in remission.

A cytoplasmic particulate fraction from human leukemic cells has been shown to contain reverse transcriptase and its associated high-molecular weight RHA template. We attempted to detect the reverse-transcriptase-template complex in morphologically normal peripheral blood leukocytes from patients with acute leukemia in complete remission. Our assay system consisted of a velocity glycerol gradient and cesium sulfate equilibrium gradient analysis of the endogenous reverse transcriptase reaction product. Three of nine patients in remission had positive reactions determined by glycerol gradient analysis, and eight of 10 patients in remission had positive reactions by cesium sulfate gradient analysis. We were unable to detect the template complex in leukocytes of normal persons. Thus, normal-appearing leukocytes in the peripheral blood of some leukemia patients in remission seem to retain a number of biochemical characteristics, possibly viral related, associated with leukemic cells.

Adult↗