Abstract
In polyoma-infected mouse kidney cell cultures 5S RNA synthesis began to increase around 16 h, i.e. 7-9 h after the onset of polyoma T-antigen synthesis. The rate of polyoma-induced 5S RNA synthesis reached a maximum plateau around 25 h when it was 1.8-2.0 times higher than in mock-infected parallel cultures. Stimulation of 5S RNA synthesis in vivo thus coincided in time with the increase in total cellular RNA and protein. Cell-free extracts (S100) prepared at 15 h from mock-(S100-M) or polyoma-infected (S100-Py) mouse kidney cell cultures were indistinguishable with respect to protein concentration and 5S RNA synthesis, using a cloned somatic Xenopus borealis 5S gene as template. S100-Py extracted 25 h after infection contained 30% more protein and synthesized 1.5-2.0 times more 5S RNA than S100-M. Complete removal of the polyoma T-antigens from S100-Py by 3 cycles of immunoprecipitation with hamster anti-T serum remained without effect on stimulated 5S RNA synthesis. However, a linear relationship between 5S RNA synthesis and protein concentration of S100-M and S100-Py was observed.
Highlights
In quiescent mouse or monkey kidney tissue culture cells arrested in phase Go/Gl of the mitotic cycle synthesis of polyoma- or SV4O- T-antigens, respectively, is followed by a mitotic host response [1]; it comprises stimulation of overall cellular RNA and protein synthesis (2; Matter, J.-M., Khandjian, E.W. and Weil, R. , unpublished results), the activation of the cellular DNA-synthesizing apparatus and the duplication of the host cell chromatin (S-phase)
Cell-free extracts (S100) prepared at 15 h from mock-(S100-M) or polyoma-infected (SlOO-Py) mouse kidney cell cultures were indistinguishable with respect to protein concentration and 5S RNA synthesis, using a cloned somatic Xenopus borealis 5S gene as template
The transcription in vitro of cloned Xenopus borealis 5S genes apparently reflected the in vivo situation
Summary
In quiescent mouse or monkey kidney tissue culture cells arrested in phase Go/Gl of the mitotic cycle synthesis of polyoma- or SV4O- T-antigens, respectively, is followed by a mitotic host response [1]; it comprises stimulation of overall cellular RNA (hnRNA, rRNA, tRNA and 5S RNA) and protein synthesis (2; Matter, J.-M., Khandjian, E.W. and Weil, R. , unpublished results), the activation of the cellular DNA-synthesizing apparatus and the duplication of the host cell chromatin (S-phase). Unpublished results), the activation of the cellular DNA-synthesizing apparatus and the duplication of the host cell chromatin (S-phase). In lytic infection virus-induced S-phase is paralleled by the production of progeny virus and is followed by cell lysis. The early events of infection, including the activation of the DNA-synthesizing apparatus, URL Pros Limited, Oxford, England. In the present work we measured polyoma-induced stimulation of 5S RNA synthesis in primary mouse kidney cell cultures; from parallel cultures we prepared cell free-extracts (S100) and studied the effect of the polyoma T-antigens on transcription in vitro of a cloned somatic 5S gene from Xenopus borealis [6,7]
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