Alterations in surface glycoproteins and level of sialyltransferase of cells transformed by a temperature-sensitive mutant of simian virus 40.

Abstract

Mouse cells transformed by a temperaturesensitive mutant of simian virus 40 belonging to complementation group A lost their ability to regulate cell growth when grown at the permissive temperature (350) but showed the low saturation density of cell growth at the restrictive temperature (39.50) Biochemical analysis of virus-transformed cells and normal cells has led many to consider that the cell surface plays an important role in the regulation of cell growth (1-6).We cannot, however, answer the following two basic questions at the present moment. First, how is the gene function of the virus involved in alterations of the structure and function of the plasma membrane, and, second, by what mechanism do the alterations in cell surface lead to the loss of cell growth regulation in vitro.In recent years, there has been an avid search for temperature-sensitive (ts) mutants of tumor viruses that induce transformation under certain conditions. Successful isolations of the mutants have been reported and have provided an intriguing system enabling correlation between gene functions and transformation on the molecular level (for a review, see ref.We have isolated several clones of mouse cells transformed by a ts A mutant of simian virus 40 (SV40) at the permissive temperature and have compared their growth patterns at the permissive and the restrictive temperatures. The clones lost cell growth regulatory functions at the permissive temperature, whereas they reverted and appeared to possess the growth characteristics of normal cells at the restrictive temperature. Other investigators have reported similar results (8-12).Furthermore, Brugge and Butel (10) showed that cells transformed by the ts A mutants exhibited the phenotype of untransformed cells at the restrictive temperature (e.g., the uptake of 2-deoxyglucose and the expression of cell surface antigen) in contrast with that of transformed cells at the permissive temperature. This finding suggests that the gene A function of SV40 may lead to the biochemical alterations of the cell surface.We wish to report that the changes in glycoproteins of the plasma membrane and the level of sialyl transferase are temperature dependent in cells transformed by the ts A mutant. MATERIALS AND METHODSVirus and Cells. The wild-type virus was derived from the small plaque 777 strain of SV40 by cloning and a mutant, tsA900, was derived from the wild-type virus after mutagenesis with UV irradiation (13). The mutant was classified into theA complementation group using tsA58, tsBl, and tsBll as references. (The reference mutants were kindly provided by P. Tegtmeyer.) A clonal line of C3H-2K mouse cells (14), C3H-2K-C4, was established at 39.5°. The W-2K-1 line was a clonal cell line transformed by the wild-type SV40 and the 900-2K-34 line was a line transformed by the tsA9W0. Each cell line was derived from a focus produced on a monolayer of the C3H-2K-C4 cells at 350 by the method described previously (13) and recloned from a colony in soft agar medium (15). Virus rescued from ea...

Altered Kinetic Properties of Sialyl and Galactosyl Transferases Associated with Herpes Simplex Virus Infection of GMK and BHK Cells

“…Viral modification of synthesis of host glycoconjugates by means of the production of virus-specific enzymes has been demonstrated for e phage infection of Salmonella anatum (Losick & Robbins,I967). The level of sialyl transferase of SV4o-transformed C3H mouse cells is reported to be under the control of the gene A function of the SV4o virus genome (Onodera et al 1976 ) but the same Km (23"8/tM) was recorded for both transformed and untransformed cells. We found that the magnitude of the apparent Km values observed for sialyl transferases and galactosyl transferases of both uninfected and HSV-infected cells were in accord with Km values of particulate glycosyl transferase activities reported for other biological systems (Onodera et al 2976;Podolsky et al I977).…”

Sialic acid changes in Dalton's lymphoma-bearing mice after cyclophosphamide and cisplatin treatment

“…The increase of sialic acid in Daltons lymphoma cells may be due to enhanced activity of enzymes involved in sialic acid synthesis and/or transfer. Some reports have indicated a 3-5 times increased sialyl transferase activity in various virally transformed cells as compared to the corresponding normal cells, an event that may be associated with the increase in the amount of sialic acid in the transformed cells (13). The elevated sialic acid levels in malignant cells have also been observed for murine Yoshida ascites sarcoma (11).…”

“…It has been reported that with the progression of tumour development there is an increase in sialic acid content of Yoshida ascites sarcoma cells (11). Although elevated levels of sialic acid have been often associated with malignancy (12), a clear correlation of changes in sialic acid concentrations and malignancy has not emerged, because some reports (13) have shown a decrease and not an increase in sialic acid in association with malignancy. Thus, evaluation of sialic acid changes could be very helpful by contributing both to the diagnosis of patients and to monitoring their progression and response to treatment.…”

Newly Synthesized Glycoproteins in Plasma Membranes of Cells Transformed by SV40 and Its Gene A Function

“…In the previous papers (Onodera et al 1976; Aoi 1978), we reported that the level of sialyltransferase activity was lowered at non-permissive temperature and the effect of Ara C was not observed. Thus , the observed changes in the level of microsomal sialyltransferase activity were not due to the progression of cells as well as those of newly synthesized glycoproteins.…”