TRANSCRIPT LEVELS OF THYMOSIN BETA-4, AN ACTIN-SEQUESTERING PEPTIDE, IN CELL-PROLIFERATION

Thymosin beta4 (beta4) is an ubiquitous 5-kDa peptide that has been identified as an actin-sequestering peptide. In this work, Northern blot analysis was used to study the beta4 mRNA levels during the cell cycle of rat thymocytes and hepatocytes as well as in human lymphocytes from patients with leukemia. Beta4 mRNA was found in all the stages of thymocyte and hepatocyte cell cycle, showing an increase in the S-phase which was mantained during the G2 and M phases. Incubation of splenic T-cells with concanavalin A, phorbol myristate acetate or the ionophore A23187 lead to a similar increase of beta4 transcript during the S-phase. The increase in beta4 mRNA observed in the G2/M boundary of the cell cycle, together with its ability to inhibit actin polymerization, suggests a possible role of beta4 in the the morphological changes and actin redistribution ocurring during the cytokinesis.