Resting state in normal and simian virus 40 transformed Chinese hamster lung cells.

Abstract

Normal cells deprived of amino acids or serum factors enter a resting state, whereas cells transformed by wild-type simian virus 40 do not. The ability to enter a resting state is temperature-sensitive (ts) in cells transformed by a tsA mutant of simian virus 40. We show further: (i) that when complete medium is added to resting cells, the length of time until the onset of DNA synthesis often exceeds the length of GI in growing cells; (ii) that the length of this interval depends upon the conditions used to arrest cell growth; but (iii) that transferring cultures from medium depleted for one factor to medium depleted in a second factor never leads to a round of DNA synthesis; and (iv) that DNA synthesis does not resume rapidly when a resting culture of cells transformed by the tsA mutant is transferred to the permissive temperature in suboptimal medium. A model proposing that in suboptimal conditions cells leave the cell cycle and traverse a branch pathway to enter the resting state is consistent with these findings. The A gene of simian virus 40 (SV40) that encodes the "Tantigen" (1, 2) is required for the initiation of viral DNA synthesis and the induction of host DNA synthesis in permissive cells (3)(4)(5), and for the maintenance of transformation in nonpermissive cells (6-10). It has therefore been proposed that transformation is a direct consequence of the aberrant initiation of host DNA synthesis by the A gene product (11,12). This view has been criticized. (i) "The critical difference between transformed and untransformed cells is that the untransformed cells go into a resting state when conditions are not optimal for their growth. Transformed cells continue to grow in such conditions. Transformation is thus an abrogation of the resting state ... (ii) ... The point in the cell cycle at which cells rest is somewhere in G1 but not at the border of the S phase ... (iii) ... Therefore, it would appear that transformation is not a process involving the control of DNA synthesis" (13). The data in this paper support assertion (i), but cast doubt on assertion (ii), and hence on the conclusion (iii).A considerable body of literature (e.g., refs. 14-16) suggests that cells enter a resting state when the culture medium becomes depleted either by the intentional removal of a nutrient or at high cell densities because the growing cells consume some growth factor (17). The resting state, Go, has been localized to that portion of the cell cycle in which the cell contains an unreplicated genome (14-16). However, considerable controversy exists over the precise location of Go. Some authors have proposed that resting states exist throughout the CI phase of growth, "early-, mid-, or late-C1" blocks (18). Others (14,19) have proposed that Go lies outside the cell cycle, but have not specified how such a state is reached. Pardee (20) (6,11,15). Dulbecco-Vogt modified Eagle's medium (National Institutes of Health media supply) was supplemented with penicillin and streptomycin (6), 5 X 10-6 M thymidine [and where indic...

Specific early-G1 blocks accompanied with stringent response in Saccharomyces cerevisiae lead to growth arrest in resting state similar to the G0 of higher eucaryotes.

“…Arrests produced by cdc28 or cdc24 mutations or a-factor block belong to the second type. The type 1 arrest appears to be similar to the state of cells previously designated as Go or the resting state in cultured mammalian and avian cells (1,19,25,40). Using cultured human fibroblasts, Augenlicht and Baserga (1) have found that a lag before the onset of DNA synthesis elongated when cells that had been arrested for longer periods were stimulated.…”

“…A distinctive property of cultured cells existing in Go may be an unusually long delay between the shift of the culture from nonpermissive to permissive conditions for growth and the initiation of DNA synthesis (1,25). Recently, we observed that lymphocytes that had divided recently responded quickly to a stimulus, but lost this ability and became cells that responded slowly when incubated in the absence of the stimulus (19).…”

“…Second, there would be another type of specific arrests that do not affect the mode of restimulation irrespective of the time that cell proliferation has been restricted. We refer to the first type as Go arrest because ofthe similarity of the arrested yeast cells to Go fibroblasts and other cultured cells (1,25) and Go lymphocytes (19). In addition, we have noted that G, arrests leading to Go state were always accompanied with a stringent response ofmacromolecular synthesis.…”

Synthesis of labile, serum-dependent protein in early G 1 controls animal cell growth

“…The role of R point control is accentuated by studies of cells transformed to tumorigenicity by DNA tumor viruses (8)(9)(10). Whereas nontumorigenic cells become quiescent within one generation after the serum concentration is reduced, these transformed cells have lost their growth control and grow in media containing very low concentrations of serum.…”

Hormonal regulation of the transformation phenotype in simian virus 40-transformed rat embryonic preadipose cell lines.

“…Simian virus 40 (SV40), a DNA tumor virus, transforms nonpermissive cells and produces cell lines, transformants, which, unlike cells transformed by RNA tumor viruses (10,23,28), are often deficient in their ability to enter the resting state, or stationary phase, at high cell density (5,10,25,29,30). SV40 transformation has been used to study differentiated functions (for a recent review, see reference 50) and to isolate functional cell lines in culture (3, 6-8, 40, 45, 46).…”