The N and C termini of the splice variants of the human mitogen-activated protein kinase-interacting kinase Mnk2 determine activity and localization.
The cap-binding eukaryotic initiation factor eIF4E is phosphorylated by the mitogen-activated protein (MAP) kinase-interacting kinases (Mnk's). Three forms of the Mnk's exist in human cells: Mnk1, Mnk2a, and Mnk2b. These last two are derived from the same gene by alternative splicing and differ only at their C termini. While Mnk2a contains a MAP kinase-binding site in this region, Mnk2b lacks such a sequence and is much less readily activated by MAP kinases in vitro. Expression of Mnk2b in mammalian cells leads to increased phosphorylation of eIF4E, showing that it acts as an eIF4E kinase in vivo. While Mnk2a is cytoplasmic, a substantial amount of Mnk2b is found in the nucleus. Both enzymes contain a stretch of basic residues in their N termini that plays a role in binding to eIF4G and functions as a nuclear localization signal. Binding of eIF4G or nuclear import appears to be regulated by the C terminus of Mnk2a. Furthermore, the MAP kinase-binding site of Mnk2a regulates nuclear entry. Within the nucleus, Mnk2b and certain variants of Mnk2a that are present in the nucleus colocalize with the promyelocytic leukemia protein PML, which also binds to eIF4E.
Scheper
Gert C
GC
Division of Molecular Physiology, Faculty of Life Sciences, University of Dundee, Dundee, United Kingdom.
Parra
Josep L
JL
Wilson
Mary
M
Van Kollenburg
Barbara
B
Vertegaal
Alfred C O
AC
Han
Ze-Guang
ZG
Proud
Christopher G
CG
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D001665:Binding Sites; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D039561:Eukaryotic Initiation Factor-4E / Q000378:metabolism; D039603:Eukaryotic Initiation Factor-4G / Q000737:chemistry; D017353:Gene Deletion; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D047908:Intracellular Signaling Peptides and Proteins; D007525:Isoelectric Focusing; D020935:MAP Kinase Signaling System; D008856:Microscopy, Fluorescence; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009154:Mutation; D009363:Neoplasm Proteins / Q000378:metabolism; D009687:Nuclear Proteins; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D000071156:Promyelocytic Leukemia Protein; D011485:Protein Binding; D020033:Protein Isoforms; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000235:genetics*; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013347:Subcellular Fractions; D013997:Time Factors; D014157:Transcription Factors / Q000378:metabolism; D014162:Transfection; D025521:Tumor Suppressor Proteins
D039561:Eukaryotic Initiation Factor-4E; D039603:Eukaryotic Initiation Factor-4G; D047908:Intracellular Signaling Peptides and Proteins; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D000071156:Promyelocytic Leukemia Protein; D020033:Protein Isoforms; D011994:Recombinant Proteins; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; C070576:PML protein, human; D005982:Glutathione Transferase; C486342:MKNK2 protein, human; D017346:Protein Serine-Threonine Kinases