DIFFERENTIATION-LINKED EXPRESSION OF PROTHYMOSIN-ALPHA GENE IN HUMAN MYELOID LEUKEMIC-CELLS

Prothymosin α (ProTα) is a nuclear protein related to cell proliferation. Its gene is highly activated during postnatal development at stages containing many proliferating but also differentiating cells. In this report, a study on ProTα gene expression during differentiation of human myeloid leukemic (HL-60) cells was undertaken to analyze the possible association of ProTα to cell differentiation. When HL-60 cells were induced to differentiate to granulocytes (using retinoic acid) or monocyte/macrophages (using 12-O-tetradecanoylphorbol-13-acetate), a marked down-regulation in the levels of ProTα transcript was found. When cell division of immature HL-60 cells was interrupted by either treatment with hydroxyurea or serum starvation, ProTα gene expression was not significantly altered. These findings suggest that loss of ProTα mRNA in induced HL-60 cells is a differentiation-related event. Examination of the stability of ProTα mRNA showed that the stabilization of the ProTα transcript is differentially regulated in the two HL-60 lineages. Nuclear run-on experiments revealed that during HL-60 differentiation, the transcriptional activity of the ProTα gene does not experience significant variations. © 1993 Academic Press, Inc.