UP-REGULATION OF JUN AND FOS FAMILY MEMBERS AND PERMANENT JNK ACTIVITY LEAD TO CONSTITUTIVE AP-1 ACTIVATION IN THEILERIA-TRANSFORMED LEUKOCYTES

Theileria parasitises bovine leukocytes and transforms them into proli ferating, metastatic tumours, where the infection resembles a leukaemi a-like disease. We have studied the signal transduction pathways leadi ng to activation of the transcription factor AP-1 in different transfo rmed leukocytes. Parasite infection leads to an up-regulation of all m embers of the Jun/Fos family of proteins and surprisingly, this occurs in the absence of any detectable ERK, or p38 MAP kinase activity. In the parasitised B-sarcoma TBL3, AP-1 induction occurs in the absence o f any JNK activity. In contrast, in infected macrophage and B-cell lin es, AP-1 transcriptional activity is strictly associated with the para site-induced constitutive activation of JNK and subsequent c-Jun N-ter minal phosphorylation. Thus, constant AP-1 transcriptional activity in volves both an upregulation in the levels of Jun and Fos proteins and constitutive JNK activation. (C) 1998 Elsevier Science B.V. All rights reserved.