The role of large T antigen in simian virus 40-induced reactivation of silent rRNA genes in human-mouse hybrid cells

Soprano, Kenneth J.; Rossini, Mara; Croce, Carlo M.; Baserga, Renato

doi:10.1016/0042-6822(80)90099-9

Cited by 29 publications

(18 citation statements)

References 19 publications

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“…Either these activities reflect different functions of the protein or activation of rRNA genes requires an additional activity. Reactivation of rRNA genes, as previously reported (9,(32)(33)(34), was an all-or-none phenomenon. A detectable peak of mouse 28S rRNA was either clearly present (+ in Table 2) or totally absent (-in Table 2).…”

Section: Discussionmentioning

confidence: 49%

“…One of the biological activities of the large T antigen in the infected host cells is stimulation of cell division (see reference 40 for a review). This mitogenic activity is accompanied by stimulation of cellular DNA and rRNA syntheses (4,9,12,13,30,31,34,39 Reactivation of silent rRNA genes. Soprano et al (33) have previously shown that microinjection of the T-antigen gene is capable of reactivating silent mouse rRNA genes in the humanmouse 55-54 hybrid cells.…”

Section: Methodsmentioning

confidence: 99%

“…Under standard growth conditions, these cells continuously express human rRNA. The mouse rRNA genes are repressed but can be activated by infection with SV40 (32), a variety of adenovirus-SV40 hybrid viruses (33,34), and microinjection with a variety of SV40 DNA fragments (9,33).…”

Section: Methodsmentioning

confidence: 99%

“…The results (together with previous reports) indicate that the critical sequences for these three functions are located separately on the simian virus 40 A gene, as follows: (i) As summarized in the preceding paper (26), genetic and biochemical evidence indicates that the early region of the simian virus 40 (SV40) genome is required for many of the biological activities of the virus. This region is needed for viral DNA replication (35), autoregulation of early genes (1, 14, 29, 38), cell transformation (2,3,15,16,18,23,37), and stimulation of cellular DNA and RNA syntheses (4,9,12,13,19,22,27,30,31,34,39). Although the early region codes for two proteins, the large T antigen (containing 708 amino acids) and the small t antigen (containing 174 amino acids), most of these functions have been attributed to the large T antigen.…”

mentioning

confidence: 99%

“…This region is needed for viral DNA replication (35), autoregulation of early genes (1,14,29,38), cell transformation (2, 3, 15,16,18,23,37), and stimulation of cellular DNA and RNA syntheses (4,9,12,13,19,22,27,30,31,34,39). Although the early region codes for two proteins, the large T antigen (containing 708 amino acids) and the small t antigen (containing 174 amino acids), most of these functions have been attributed to the large T antigen.…”

mentioning

confidence: 99%

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Mutational analysis of simian virus 40 T antigen: stimulation of cellular DNA synthesis and activation of rRNA genes by mutants with deletions in the T-antigen gene.

Soprano¹,

Galanti²,

Jonak³

et al. 1983

Mol. Cell. Biol.

108

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The biological activity of several deletion mutants of simian virus 40, cloned in pBR322, was determined. Three functions of the simian virus 40 A gene were studied: (i) the ability to express T antigen; (ii) the ability to induce cell DNA replication; and (iii) the ability to reactivate silent rRNA genes in hybrid cells. Recombinant plasmid DNA was introduced into cells by manual microinjection or by transfection. The results (together with previous reports) indicate that the critical sequences for these three functions are located separately on the simian virus 40 A gene, as follows: (i) As summarized in the preceding paper (26), genetic and biochemical evidence indicates that the early region of the simian virus 40 (SV40) genome is required for many of the biological activities of the virus. This region is needed for viral DNA replication (35), autoregulation of early genes (1, 14, 29, 38), cell transformation (2,3,15,16,18,23,37), and stimulation of cellular DNA and RNA syntheses (4,9,12,13,19,22,27,30,31,34,39). Although the early region codes for two proteins, the large T antigen (containing 708 amino acids) and the small t antigen (containing 174 amino acids), most of these functions have been attributed to the large T antigen. As is true of many other proteins which exhibit multiple functions (for a review, see reference 17), some of the functions of the large T antigen can be localized to specific domains. These domains can be determined in some detail by studying the functions of modified, cloned SV40 DNAs introduced into the nuclei of cells by the manual microinjection technique of Graessmann and Graessmann (10). By microinjecting fragments of SV40 DNA, Galanti et al. (9) have previously been able to distinguish those sequences in the T-antigen gene that are critical for the stimulation of cell DNA replication from those that are critical for the activation of silent rRNA genes. In the present communication we report further experiments in which this technique was applied to the cloned deletion mutants of SV40 described in the preceding paper (26) to refine the map positions of T-antigen coding regions involved in these two activities. MATERIALS AND METHODSGrowth and preparation of cells. tsl3 cells, a Glspecific temperature-sensitive mutant originally derived from BHK cells (20), were grown at 34°C on glass cover slips as previously described. Before microinjection, tsl3 cells were made quiescent by allowing them to grow for 7 days in Dulbecco minimal essential medium supplemented with 1% calf serum. After microinjection, cells were incubated at 340C for 24 h in the same medium supplemented with [3H]thymidine (0.7 ,Ci/ml). All media were warmed to the temperature of incubation before use.

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Section: Discussionmentioning

confidence: 49%