Abstract
Previous studies have shown that activation of the Raf/MEK/ERK pathway is necessary for G2/M transition. However, as for the activation state of MEK in mitosis the conclusion is not consistent. Here we show that MEK is inhibited in mitosis. In addition, we identify a multifunctional protein named B23 that strongly cross-reacts with a phospho-MEK antibody in mitotic cells. Sequence homology between the N-terminus surrounding Ser 4 of B23 and the Raf phosphorylation site on MEK suggests a mechanism for cross-reaction of the antibody. Thus, mutation of Ser 4 to alanine abolishes cross-reactivity between B23 and the phospho-MEK antibody. Our findings may explain the discrepancy of results obtained with the use of phospho-MEK antibody regarding the activation state of MEK in mitosis.
Publication types
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Animals
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Antibodies / immunology
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Antibodies, Phospho-Specific / metabolism
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COS Cells
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Chlorocebus aethiops
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Cross Reactions
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Enzyme Activation
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Humans
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MAP Kinase Signaling System / physiology
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Membrane Proteins / metabolism*
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Mice
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Mitogen-Activated Protein Kinase Kinases / antagonists & inhibitors*
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Mitogen-Activated Protein Kinase Kinases / genetics
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Mitogen-Activated Protein Kinase Kinases / immunology
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Mitogen-Activated Protein Kinase Kinases / metabolism*
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Mitosis*
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NIH 3T3 Cells
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Nuclear Proteins / immunology
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Nuclear Proteins / metabolism*
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Nucleophosmin
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Phosphorylation
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Serine / metabolism*
Substances
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Antibodies
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Antibodies, Phospho-Specific
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Membrane Proteins
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Npm1 protein, mouse
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Nuclear Proteins
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Nucleophosmin
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Serine
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Mitogen-Activated Protein Kinase Kinases