Characterization of MAPK activation in wild type and MEKK1-deficient cell lines.

<p><i>A</i>. Phosphorylation of c-Jun phosphorylation is defective in the <i>MEKK1</i>^−/− chicken DT40 cells in response to cytoskeletal disruption. Wild type (Wt) and <i>MEKK1</i>^−/− DT40 cells were left untreated (U) or stimulated with 1 µM vinblastine (Vin), 2 µg/ml cytochalasin D (Cy), and 90 nM okadaic acid (OA) for four hours, lysed in modified RIPA buffer and run on an SDS-PAGE gel to compare wild type and knockout cell lines. Western blot membranes were probed for phosphorylated and total c-Jun, ERK and p38. <i>B</i>. Phosphorylation of c-Jun is defective in <i>MEKK1</i>^−/− murine pre-B cells in response to cytoskeletal disruption. Wild type (Wt) and <i>MEKK1</i>^−/− pre-B murine cells were stimulated with 1 µM vinblastine, 2 µg/ml cytochalasin D, and 90 nM okadaic acid for four hours, lysed in modified RIPA buffer and run on an SDS-PAGE gel. Membranes were probed for phosphorylated and total c-Jun, ERK and p38. β-tubulin is used as loading control.