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 SV 40 do not. The ability to enter a resting state is temperature sensitive (ts) in cells transformed by a tsA mutant of SV 40. When complete medium is added to resting cells, the length of time until the onset of DNA synthesis often exceeds the length of G1 in growing cells. The length of this interval depends on the conditions used to arrest cell growth, but transferring cultures from medium depleted for one factor to medium depleted in a 2nd factor never leads to a round of DNA synthesis. 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.