Kinetic analysis of the cell cycle progression (A), [3H]TdR- incorporation (B), and PHGDH mRNA (C) of during activation of G0 T cells by immobilized anti-CD3. Murine resting T cells were activated by immobilized anti-CD3. The cells were harvested at the indicated times for cell cycle analysis, which was performed on an equal number of the cells (104) by flow cytometry after staining of DNA with propidium iodide. For [3H]TdR-incorporation assay, murine G0 T cells (105/well) were activated by immobilized anti-CD3 in a 96-well plate, and pulsed for 1 h with 1 μCi of [3H]TdR at times indicated. Each value is expressed as mean ± SD (n = 3). For Northern analysis, total RNA (10 μg) from each time point were electrophoresed, transferred, and probed with 32P-labeled PHGDH, cdc2, IL-2, IL-2Rα, IL-2Rβ, and 18S rRNA cDNA.