The cJun N-terminal kinase (JNK) signaling pathway mediates induction of urokinase-type plasminogen activator (uPA) by the alkylating agent MNNG

The monofunctional alkylating agent N-methyl-N-nitro-N-nitrosoguanidine (MN NG) is a widespread environmental carcinogen that causes DNA lesions, leadi ng to cell death. However, MNNG can also trigger a cell-protective response by inducing the expression of DNA repair/transcription-related genes. We d emonstrate that the urokinase-type plasminogen activator (uPA) gene product , a broad spectrum extracellular protease to which no DNA repair function h as been assigned, is transcriptionally induced by MNNG in C2C12 and NIH3T3 cells. This induction required an AP1-enhancer element located at -2.4 kilo base (kb), because it was abrogated by deletion of this site. MNNG was foun d to induce the activation of JNK/SAPK and p38 mitogen-activated protein ki nases (MAPKs), Accordingly, we attempted to assess the contribution of each of these MNNG-inducible MAPKs to uPA gene induction by this alkylating age nt. Coexpression of dominant negative versions of kinases of the JNK pathwa y, such as catalytically inactive forms of MEKK1, MKK7, and JNKK, and of cy toplasmic JNK-inhibitor JIP-1, as well as treatment of cells with curcumin (which blocks JNK activation by MNNG), inhibited MNNG-induced uPA transcrip tional activity. In contrast, neither dominant negative MKK6 nor SB203580, which specifically inhibit p38 MAP kinase activation, abrogated the MNNG-in duced effect. Taken together, our results show that the JNK signaling pathw ay links external MNNG stimulation and AP1-dependent uPA gene expression, p roviding the first functional dissection of a transcription-coupled signal transduction pathway for MNNG. (Blood. 2000;96:1415-1424) (C) 2000 by The A merican Society of Hematology.