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. 2004 Mar;24(6):2308–2317. doi: 10.1128/MCB.24.6.2308-2317.2004

FIG. 4.

FIG. 4.

ERK feedback inhibition of S298 phosphorylation requires T292. (A) COS-1 cells were transfected with mutant T292 forms of MEK1 Act. and either FLAG-ERK2 or ERK2 T183A. The cells were serum deprived after the transfection and were treated with either DMSO or 10 mM U0126 for the last 5 h before harvest. HA-MEK immunoprecipitates (IP) were immunoblotted with anti-HA and anti-phospho-S298 antibodies. (B) ERK phosphorylates MEK on T292. MEK1 or T292A were transfected with FLAG-Raf-CAAX and FLAG-ERK. The cells were serum deprived and treated with DMSO or U0126 as described for panel A. HA-MEK1 immunoprecipitates were immunoblotted with anti-HA and anti-phospho-MEK1 T292 antibodies.