Effects of tryptophan deprivation on L1210 cells in culture.

When murine L1210 leukemia cells growing in suspension culture are deprived of tryptophan, there is a rapid fall in DNA and histone synthesis and a less rapid fall in whole cellular protein and non-histone nuclear protein synthesis. Initially, the S phase of the cell cycle becomes prolonged, but subsequently the cells become defective in their ability to reinitiate S phase. By 24 hr complete growth arrest has occurred, at which point about 60% of the cells have a GI DNA content and 32% have a late-S-phase DNA content. Growth arrest occurs at a cell density about 1.8 times the starting density. Readdition of tryptophan at this time pro duces resumed incorporation of thymidine-3H followed by