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Fig. 2. Role of the JNK pathway in gastrin-induced DNA synthesis. A, equal amounts of cellular proteins from CHO-CCKB cells, CHO-CCKB cells overexpressing TAM67 (clones 5, 9, and 10), and CHO-CCKB cells transfected with the empty vector pCMV (pCMV) were immunoblotted with an anti-c-Jun antibody directed against the DNA-binding region of the transcription factor. B, after a 30-min preincubation with or without 10 µM SP-600125 (SP), CHO cells expressing the human CCKBR were stimulated for 5 min with 10 nM gastrin. After IP with an anti-JNK1 antibody, JNK activity using GST-c-Jun-(1–79) as an exogenous substrate was assayed as described in "Materials and Methods." C, after a 30-min preincubation with or without 10 µM SP-600125 (SP), CHO cells expressing the human CCKBR were stimulated for 5 min with 10 nM gastrin. Whole cell lysates were immunoblotted with an anti-phospho-Thr202 and -Tyr204 ERK antibody. Comparable amounts of proteins were detected in immunoprecipitates or whole cell lysates of all of the above-mentioned experiments (data not shown). D, [3H]thymidine incorporation was measured, as described in "Materials and Methods," in CHO-CCKB cells, CHO-CCKB cells transfected with the empty vector pCMV (pCMV), CHO-CCKB cells overexpressing TAM67 (clones 5, 9, and 10), and CHO-CCKB cells pretreated with 10 µM SP-600125 (SP). The results are means ± SE of three experiences performed in triplicate.