Fig. 1. A, cell cycle distribution of control (con) and elutriated NCI-H460 cells as measured by propidium iodide staining of cellular DNA. FACS profiles for elutriator fractions enriched for early G1-phase cells (fraction 2), late G1-phase cells (fraction 5), S-phase cells (fraction 8), and G2-M-phase cells (fraction 11) are presented. Successive elutriator fractions contain cells of increasing size and cell cycle transit, beginning with small, early G1-phase cells. B, expression of cell cycle-regulatory proteins in asynchronous (con) and synchronous populations of NCI-H460 cells isolated by centrifugal elutriation (fractions 2–13). Protein extracts were prepared from each fraction, and equal amounts of protein were analyzed by Western blotting with antibodies to the indicated cell cycle regulators, using actin as a loading control.