Functional analysis of the 5′ region of the β₃ gene in K562 cells. The insert at the lower left shows flow cytometry analysis of K562 cells. Fluorescence (FL) is shown on a logarithmic scale on the x-axis; cell number is shown on the y-axis. Dashed lines are the results using MoAb T10, which is specific for human _IIbβ₃. A restriction enzyme map with positions relative to the transcription start site of the β₃ gene is shown above. Reporter gene constructs containing portions of the 1,159 bp upstream of the transcription start site were transiently transfected into K562 cells and assayed for reporter activity. The reporter gene used in these studies included both CAT and luciferase, and equivalent results were obtained with both reporters. Fold increase and the standard error of the mean over the promoterless construct (background) are indicated. The number of times each construct was tested is shown in parentheses. The Materials and Methods describes how values were normalized, emphasizing the importance of the relative changes, not the absolute fold increase.