MITOGEN ACTIVATION OF HUMAN PERIPHERAL T-LYMPHOCYTES INDUCES THE FORMATION OF NEW CYCLIC-AMP RESPONSE ELEMENT-BINDING PROTEIN NUCLEAR-COMPLEXES

A large body of evidence indicates that experimental agents which rais e cellular cAMP levels inhibit T cell growth and division. By contrast , many studies have reported that mitogen activation of T cells increa ses cAMP levels, implying a positive physiological role for cAMP in th e activation process. In the present study we demonstrate that mitogen activation of human peripheral T lymphocytes induces nuclear factors that form complexes with cyclic AMP response element-binding protein ( CREB). Four complexes are identified by the electrophoretic mobility s hift assay, two of which are induced by mitogen activation. All four c omplexes contain CREB and are bound to the cAMP response element (CRE) core sequence (TGACGTCA), as indicated by antibody and oligonucleotid e competition experiments. Binding of the four complexes to CRE is pre vented by dephosphorylation of nuclear extracts and is restored by rep hosphorylation with cAMP dependent protein kinase or endogenous kinase s. Similar complexes are detected in nuclear extracts of Jurkat cells. Mitogen induction of the electrophoretic mobility shift assay complex es is not accounted for by protein phosphorylation or by induction of CREB. Rather, the data indicate that mitogen increases the levels of a nuclear factor(s) that dimerizes with CREB. Induction of new CREE com plexes implies a physiological role for cAMP in mitogen activation of T lymphocytes.