PubMed · 201849
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F H Portugal. 1977-09-15. Cell transformation with herpes simplex viruses.. https://doi.org/10.1038/269196a0
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The expression of superoxide dismutases (SOD) 1 and 2 was studied in 4 clones of human fibroblasts after their infection by simian virus 40 (SV40), in parallel with the alterations of chromosomes 21 and chromosome 6q arms, carrying the genes that encode for SOD1 and SOD2 respectively. For all clones, a similar scheme with 2 main phases was observed for both chromosome and SOD variations. The first phase, defined as the pre-crisis phase, was characterized by chromosomal instability, but maintenance of normal numbers of chromosome 6q arms and chromosomes 21. The level of SOD2 mRNA was high, while SOD2 activity and immunoreactive protein were low. SOD1 protein and activity were decreased. In the second phase, defined as the post-crisis phase, the accumulation of clonal chromosomal rearrangements led to the loss of 6q arms, while the number of chromosomes 21 remained normal. SOD2 mRNA level was decreased and SOD2 immunoreactive protein and activity remained low. SOD1 protein and activity increased with passages, reaching values similar to those of control cells at late passages. As in established SV40-transformed human fibroblast cell lines, good correlation was found between SOD2 activity and the relative number of 6q arms. These results allow us to reconstruct the sequence of events leading to the decrease of SOD2, a possible tumor-suppressor gene, during the process of SV40-transformation of human fibroblasts.
The major surface protein of hepatitis B virus produced in Saccharomyces cerevisiae can be recovered from cell lysates in the form of 22-mm lipoprotein particles. Immunoelectron microscopy was applied to investigate site and time of particle assembly. Thin sections of yeast cells revealed that production of the S protein provoked a dilation of the endoplasmic reticulum. Dilated areas were specifically labeled with a polyclonal antibody raised against glutaraldehyde-treated yeast-derived HBsAg particles. In contrast to previous postulates of particle formation during cell lysis and extract preparation, these results suggest that particle formation in yeast occurs in the endoplasmic reticulum and that transport of particles along the secretion pathway is blocked.
The effect of interferon-gamma (IFN-gamma) on epidermal growth factor (EGF) receptor binding and the proliferation of normal and simian virus 40 (SV40)-transformed human fibroblast cells was compared under identical culture conditions. IFN-gamma induced an enhancement of EGF binding to normal cells, whereas it decreased the EGF binding to SV40-transformed cells. Half-maximal enhancement occurred at 72 h after the normal cells were exposed to 10 U/ml of IFN-gamma, and maximal stimulation was obtained at about 10(2) U/ml of IFN-gamma at 72 h. On the other hand, half-maximal reduction was observed for SV40-transformed cells at less than 10 U/ml of IFN-gamma at 72 h, and maximal reduction was obtained at around 10(3) U/ml of IFN-gamma at 72 h. Scatchard analysis indicated that the number of EGF binding sites of normal and SV40-transformed cells was calculated to be 1.6 x 10(5) and 0.88 x 10(5) per cell, respectively, and was little altered by IFN-gamma treatment. The dissociation constant (Kd) of normal cells, however, decreased from 4.5 nM (control) to 2.0 nM (IFN-gamma-treated), while the Kd of SV40-transformed cells increased from 3.6 nM (control) to 17.0 nM (IFN-gamma-treated). The immunoprecipitation of 125I-labeled EGF-bound EGF receptors with anti-receptor antiserum indicated that a 72-h IFN-gamma treatment did not induce a conformational alteration in the EGF receptors of both normal and transformed cells. The DNA synthesis of normal cells was enhanced by EGF, and IFN-gamma treatment potentiated the effect of EGF on DNA synthesis, probably due to the increased binding affinity of EGF to the cells.(ABSTRACT TRUNCATED AT 250 WORDS)