IDENTIFICATION OF BETA-ACTIN SEQUENCES NECESSARY FOR INDUCTION BY PHORBOL ESTERS AND CALCIUM IONOPHORES

Transcription of the cytoskeletal beta-actin gene is rapidly induced b y phorbol 12-myristate 13-acetate (PMA) and the calcium ionophore, A23 187, in cultured H4IIE hepatoma (H4) cells. PMA directly activates pro tein kinase C (PKC) and activation of PKC is necessary for the cellula r actions of PMA, including induction of beta-actin gene transcription . In the present study, we determined the DNA sequence requirements fo r induction of the beta-actin gene by PMA and A23187. Constructs conta ining progressive deletions of normal and mutated human beta-actin 5' sequences fused to the reporter gene, bacterial chloramphenicol acetyl transferase, were analysed in transient transfections of H4 cells. We delineated the PMA response DNA element of the human beta-actin gene t o the proximal CCArGG box (-62 to -53) in the 5' flanking region. In c ontrast, A23187 did not induce expression of transfected gene construc ts containing this CCArGG box. Additionally, we demonstrated that CCAr GG boxes from two other PMA-induced genes in H4 cells, c-fos and gamma -actin, could confer PMA inducibility to a heterologous promoter. This CCArGG box specifically interacts with one or more proteins present i n nuclear extracts of H4 cells. These results indicate that in culture d cells, PMA-dependent induction of the beta-actin gene is mediated th rough the proximal CCArGG box. This suggests that the CCArGG box is a target for PKC action and may be involved in the control of other PKC regulated genes.