[Possible role of the T antigen in inducing chromosome aberrations in SV40 virus-transformed cells]. / Vozmozhnaia rol' T-antigena v induktsii khromosomnykh aberratsii v kletkakh, transformirovannykh virusom SV40.

A possible role of the simian virus 40 T antigen in chromosome damages in transformed cells was examined. Two lines of Golden hamster embryonal fibroblasts, transformed by SV40 tsA30 and ts239 mutants (He30 and He239, respectively), were incubated at nonpermissive (40.5-41 degrees C) or permissive (33 degrees C) temperatures. Chromosome aberrations were registered in either subline after 3, 6, 9 and 12 weeks of cultivation under the above conditions. In the both cell lines kept at 33 degrees the frequency of aberrant metaphases and the number of chromosome breaks per cell increased drastically by week 3 of cultivation, and such a state was preserved up to week 12. The frequency of aberrant metaphases in cells cultivated at 41 degrees was maintained at the constant level (He239) or at slightly higher than that in the original culture (He30). The sublines He239, originally incubated at 33 or 40.5 degrees, were then shifted to 40.5 and 33 degrees, respectively. As a result the number of chromosome aberrations either decreased (33----40.5 degrees) or increased (40.5----33 degrees) as early as on day 2, and these patterns were stabilized at the level corresponding to the new conditions. We assayed the induction of DNA breaks in cells, grown at the permissive or nonpermissive temperatures, by using DNA sedimentation in the alkaline sucrose gradient. The DNA sedimentation peaks of cells cultured at 37 and 41 degrees coincided, whereas the DNA of cells cultured at 33 degrees was represented by shorter fragments.

[Induction of the replicative synthesis of DNA by SV40 virus T antigen introduced into cells using liposomes]. / Induktsiia replikativnogo sinteza DNK T-antigenom virusa SV40, vvedennogo v kletki s pomoshch'iu liposom.

The role of virus SV40 T-antigen in the induction of cell DNA synthesis during its incorporation into cell liposomes was studied, using monolamellar liposomes obtained by phase reversal with incorporated highly purified T-antigen. Immunofluorescence studies revealed that T-antigen effectively penetrates inside the cells and after 10 hours is accumulated in the nuclei, where its level remains unchanged for 24 hours. Injections of purified T-antigen into the renal cells of serum-starved CV1 monkeys resulted in an almost 10-fold increase in the number of DNA-synthesizing cells 18 hours after the exposure. The same effect was observed during stimulation of a 10% serum culture. Removal of T-antigen from the preparation by specific immunoadsorption eliminated this effect. Centrifugation of cells grown in the presence of bromodeoxyuridine in a CsCl gradient was used to demonstrate the replicative type of cell DNA synthesis during T-antigen induction.