Abstract
Antigen-stimulated human T lymphocytes must bind the immunoregulatory hormone interleukin 2 (IL-2) if they are to transit from the G1 to the S phase of the cell cycle. Indirect methods, such as the measurement of thymidine uptake rates, were previously the only means available for exploring the mechanism of action of IL-2. Several cDNA clones have been isolated which are expressed subsequent to IL-2 binding, and the expression of two of these genes. Tact52 and Tact75, is regulated directly at the level of transcription; expression of the proto-oncogene c-myb is also regulated directly by IL-2 binding. These genes thus constitute a set which is coordinately regulated in the course of the transition from G1 to S phase of human T lymphocytes, and their expression depends on IL-2 binding.