Polyadenylic acid metabolizing enzyme levels during induction of differentiation in a human leukemia T-cell line with phorbol ester.

Induction of differentiation of MOLT3 cells with 12-O-tetradecanoylphorbol-13-acetate (TPA) was found to affect the activity levels of the polyadenylic acid [poly(A)] metabolizing enzymes. TPA administration at a concentration of 16 nM resulted in an increase of poly(A) exonuclease and poly(A) polymerase activities after 2 and 2.5 hours, respectively, and in a decline to control levels thereafter. Cordycepin, an inhibitor of poly(A) polymerization, prevented the increasing binding of OKT11A monoclonal antibody induced by TPA treatment, whereas TPA-induced reduction in OKT6 monoclonal antibody binding persisted. The alterations in the poly(A) metabolizing enzyme activities following treatment of the cells with TPA, as well as the inhibitory effect of cordycepin, may suggest that these enzymes may be involved in the regulation of the differentiation process.