Rous AT - Academia.edu (original) (raw)

Papers by Rous AT

Proceedings of The National Academy of Sciences, 1982

We characterized the transcriptional activity of the long terminal repeat (LTR) of Rous sarcoma v... more We characterized the transcriptional activity of the long terminal repeat (LTR) of Rous sarcoma virus by constructing a recombinant plasmid, pRSVcat, in which bacterial chloramphenicol acetyltransferase (CAT; acetyl-CoA:chloramphenicol 3-0-acetyltransferase, EC 2.3.1.28) coding sequences are placed under LTR control. We find that the LTR directs relatively high levels of CAT synthesis within 48 hr after calcium phosphate-mediated introduction of this plasmid into CV-1 monkey kidney cells, chicken embryo fibroblasts, Chinese hamster ovary cells, HeLa cells, or mouse NIH/3T3 cells. The level of CAT synthesis is 3-fold higher in CV-1 cells and up to 10-fold higher in HeLa and mouse NIH/3T3 cells than after transfection with a related vector, pSV2cat, carrying CAT sequences under control of the simian virus 40 early promoter. We have shown, by primer extension, that the amounts of CAT-specific mRNAs encoded by pRSVcat and pSV2cat correlate with the levels of CAT enzyme activity. By both SI nuclease mapping and primer extension, we have demonstrated that the start site for RNA transcription within the LTR of pRSVcat corresponds to previous mapping data. We estimated transfection efficiencies by monitoring immunofluorescence induced by a rhodamine-labeled CAT antibody. Our results indicate that the Rous sarcoma virus LTR can direct synthesis of high levels of functional mRNA and has a wide expression range. The observed high transcriptional activity of the LTR is significant because it has been postulated that this LTR promotes activity of adjacent cellular oncogenes.

Journal of Experimental Medicine, 1941

Proceedings of The National Academy of Sciences, 1980

Another intracellular location of the Rous sarcoma virus (RSU) src gene product (pp6O(W) has been... more Another intracellular location of the Rous sarcoma virus (RSU) src gene product (pp6O(W) has been detected within RSV-transformed cells by indirect immunofluorescence. By using rabbit anti-tumor serum specific for pp6Os, a speckled pattern of fluorescence was found on the ventral surface of RSV (Schmidt-Ruppin strain)transformed normal rat kidney cells.

Proceedings of The National Academy of Sciences, 1973

In a culture medium of pH 7.4 and a folic acid concentration of 100 mug/liter that contains 5% he... more In a culture medium of pH 7.4 and a folic acid concentration of 100 mug/liter that contains 5% heat-inactivated chicken plasma rather than serum, the rate of proliferation of normal chicken fibroblasts is determined by the concentration of calcium. Proliferation, rapid when the calcium concentration is physiological, decreases when the calcium concentration is reduced. At a very low calcium concentration, in this culture medium, normal fibroblasts are maintained without proliferation, whereas those infected with Rous sarcoma virus proliferate rapidly. This proliferative inactivity of normal fibroblasts does not involve contact-inhibition, since the effect is observed at low, as well as higher, culture densities. When a physiological amount of calcium is added to cultures of normal fibroblasts that have been maintained in very low calcium-plasma medium for 3 days, labeled thymidine uptake and protein synthesis are strongly stimulated, and cell division follows. The use of heat-inactivated chicken serum, instead of plasma, in this medium appears to strongly sensitize normal fibroblasts to the mitogenic action of calcium. In a plasma-containing culture medium of physiological calcium concentration and a folate concentration of 5 mug/liter, neither normal nor Rous sarcoma virus-infected fibroblasts proliferate to an appreciable extent. The use of serum, however, instead of plasma results in rapid proliferation of both normal and infected cells, as does increase in the folate concentration of the plasma-containing medium to 100 mug/liter.The fact that while normal fibroblasts are maintained without proliferation in low calcium-plasma medium, Rous sarcoma virus-infected fibroblasts proliferate rapidly, indicates that the effect of calcium is regulatory rather than permissive. These results suggest that the proliferation of normal fibroblasts is initiated by a cellular function involving calcium, and that the autonomous proliferation of the neoplastic fibroblasts results either from increased calcium uptake or from an alteration or a hypass of that function. The results also suggest that serum contains a mitogenic factor(s) not present in plasma, possibly a &amp;quot;wound hormone&amp;quot; for fibroblasts.

IEEE Transactions on Power Electronics, 2005

In this study, a high step-up converter with a coupled-inductor is investigated. In the proposed ... more In this study, a high step-up converter with a coupled-inductor is investigated. In the proposed strategy, a coupled inductor with a lower-voltage-rated switch is used for raising the voltage gain (whether the switch is turned on or turned off). Moreover, a passive regenerative snubber is utilized for absorbing the energy of stray inductance so that the switch duty cycle can

Proceedings of The National Academy of Sciences, 1960

Proof: Obviously pak(i) = 0. Let n = k(p -1) + 1 and let m be an integer such that 2m -2n > i -3.... more Proof: Obviously pak(i) = 0. Let n = k(p -1) + 1 and let m be an integer such that 2m -2n > i -3. Then it follows from (B) and Lemma 3 that i ak(2m -2n + 3) = (-1)k+1(m!/p) 68m $ 0. Thus'ak(i) $ 0. q.e.d.

International Journal of Cancer, 1974

Normal chick fibroblasts are known to contain a tissue-specific surface component, a major glycop... more Normal chick fibroblasts are known to contain a tissue-specific surface component, a major glycoprotein (SF) antigen that is also present in chicken serum. This antigen was greatly reduced in amount or absent in fibroblasts transformed by five different Rous sarcoma virus strains. Fibroblasts infected with virus mutants temperature sensitive for transformation recovered the SF antigen when maintained at the non-permissive temperature. Productive infection with a non-transforming avian type-C virus did not alter the level of SF antigen characteristic of normal fibroblasts. Polyacrylamide gel electrophoresis of total cell extracts indicated that proteins with apparent mol. wt. of 145,000 and mol. wt. 210,000 were greatly decreased following transformation of the fibroblasts. That the ability to synthetize the 145,000 mol. wt. polypeptide was lost upon transformation was implied by pulse labelling experiments, in which normal fibroblasts incorporate [35S] methionine into the above polypeptide whereas transformed cells lose this ability. This polypeptide, unique in its presence in normal but not in transformed cells, appears to have an exceptionally high rate of turnover. Indirect evidence suggests that the 145,000 and 210,000 polypeptides are molecular counterparts of the SF antigen. The transformation-associated change in the quantity of the SF molecule supports our proposal that tissue-specific surface glycoproteins, such as the SF antigen, express the stage of differentiation at the membrane of normal cells and may be involved in intercellular control of growth and movement.

The internal structural proteins of retroviruses are proteolytically processed from the Gag polyp... more The internal structural proteins of retroviruses are proteolytically processed from the Gag polyprotein, which alone is able to assemble into virus-like particles when expressed in cells. All Gag proteins contain domains corresponding to the three structural proteins MA, CA, and NC. We have expressed the CA and NC domains together as a unit in Escherichia coli, both for Rous sarcoma virus (RSV) and for human immunodeficiency virus type 1 (HIV-1). We also expressed a similar HIV-1 protein carrying the C-terminal p6 domain. RSV CA-NC, HIV-1 CA-NC, and HIV-1 CA-NC-p6 were purified in native form by classic methods. After adjustment of the pH and salt concentration, each of these proteins was found to assemble at a low level of efficiency into structures that resembled circular sheets and roughly spherical particles. The presence of RNA dramatically increased the efficiency of assembly, and in this case all three proteins formed hollow, cylindrical particles whose lengths were determined by the size of the RNA. The optimal pH at which assembly occurred was 5.5 for the RSV protein and 8.0 for the HIV-1 proteins. The treatment of the RSV CA-NC cylindrical particles with nonionic detergent, with ribonuclease, or with viral protease caused disassembly. These results suggest that RNA plays an important structural role in the virion and that it may initiate and organize the assembly process. The in vitro system described should facilitate the dissection of assembly pathways in retroviruses.

Plant Ecology, 1981

The dynamics of oligotrophic pastures were analyzed in the area of El Pardo (Central Spain), and ... more The dynamics of oligotrophic pastures were analyzed in the area of El Pardo (Central Spain), and related with geomorphological features and time elapsed since the last ploughing. A sampling of the area was carried out regarding these two factors. The data were subjected to correspondence analysis, which showed the progressive replacement of species related to succession, variation along slopes, with a tight interaction between both phenomena. The correspondence between vegetation change and slope geomorphology is closer as succession progresses.