Localization of prothymosin alpha in the nucleus.

Prothymosin alpha is a widely distributed acidic protein to which an immunological function that involved its secretion was initially assigned. However, recent experiments suggest that it is a nuclear protein related to cell proliferation. To study the subcellular distribution of prothymosin alpha we have used a polyclonal antibody raised against its C-terminus. Using indirect immunofluorescence prothymosin alpha was located in the nucleus of HeLa, L929, IT-45R1, and NIH3T3 cells, mouse thymocytes, and human thymic stromal cells. The levels of prothymosin alpha mRNA were increased when the proliferation of IT-45R1 cells was induced, as has been described by others in thymocytes and NIH3T3 cells. These results show that prothymosin alpha is a nuclear protein related to cell proliferation.