Phosphorylation of Prothymosin α. An Approach to Its Biological Significance

Prothymosin alpha (ProT alpha), the precursor of the thymosin alpha(1) and thymosin alpha(11), is a 109-111 amino acids protein widely distributed in the mammalian tissues that is essential for the cell proliferation and survival through its implication on chromatin remodeling and in the proapoptotic activity. ProT alpha is phosphorylated at Thr residues by the M2 isoenzyme of the pyruvate kinase in a process that is dependent on the cell proliferation activity, which constitutes a novel dual functionality of this enzyme. The Thr residues phosphorylated are apparently dependent on the carcinogenic transformation of the cells. Thus, in normal lymphocytes residues Thr11 or Thr12 are phosphorylated in addition to a Thr7 residue, while in tumor cells Thr7 is the only residue phosphorylated. Phosphorylation of ProT alpha seems to be related to its antiapoptotic activity, although other possibilities cannot be discarded.