Prothymosin alpha promotes cell proliferation in NIH3T3 cells

Thymic hormones have immunomodulatory effects on T cells and hence have been used clinically to restore the immunity of immunodeficient patients as well as to enhance the cellular immunity of cancer patients. Prothymosin cl, which is a member of the thymic hormone family, has recently been suggested to act as a nuclear protein participating in the stimulation of cell proliferation. To characterize the biological activities of prothymosin alpha in vitro, we established NIH3T3 cell transformants that constitutively express higher prothymosin ct protein and its mRNA compared with the wild-type counterpart. Cells that overexpressed prothymosin ex increased the proliferative activity assayed by the [H-3]-thymidine incorporation or by the cell cycle analysis with the fluorescent-activate cell sorter. The results provide direct evidence that prothymosin a plays a role in cell proliferation by shortening the duration of the G1 phase.