Protein kinase CK1alpha regulates mRNA binding by heterogeneous nuclear ribonucleoprotein C in response to physiologic levels of hydrogen peroxide.
At low concentrations, hydrogen peroxide (H(2)O(2)) is a positive endogenous regulator of mammalian cell proliferation and survival; however, the signal transduction pathways involved in these processes are poorly understood. In primary human endothelial cells, low concentrations of H(2)O(2) stimulated the rapid phosphorylation of the acidic C-terminal domain (ACD) of heterogeneous nuclear ribonucleoprotein C (hnRNP-C), a nuclear restricted pre-mRNA-binding protein, at Ser(240) and at Ser(225)-Ser(228). A kinase activity was identified in mouse liver that phosphorylates the ACD of hnRNP-C at Ser(240) and at two sites at Ser(225)-Ser(228). The kinase was purified and identified by tandem mass spectrometry as protein kinase CK1alpha (formerly casein kinase 1alpha). Protein kinase CK1alpha immunoprecipitated from primary human endothelial cell nuclei also phosphorylated the ACD of hnRNP-C at these positions. Pretreatment of endothelial cells with the protein kinase CK1-specific inhibitor IC261 prevented the H(2)O(2)-stimulated phosphorylation of hnRNP-C. Utilizing phosphoserine-mimicking Ser-to-Glu point mutations, the effects of phosphorylation on hnRNP-C function were investigated by quantitative equilibrium fluorescence RNA binding analyses. Wild-type hnRNP-C1 and hnRNP-C1 modified at the basal sites of phosphorylation (S247E and S286E) both avidly bound RNA with similar binding constants. In contrast, hnRNP-C1 that was also modified at the CK1alpha phosphorylation sites exhibited a 14-500-fold decrease in binding affinity, demonstrating that CK1alpha-mediated phosphorylation modulates the mRNA binding ability of hnRNP-C.
Kattapuram
Taj
T
Department of Pathology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114, USA.
Yang
Suping
S
Maki
Jenny L
JL
Stone
James R
JR
D000595:Amino Acid Sequence; D000818:Animals; D048128:Casein Kinase Ialpha / Q000378:metabolism / Q000502:physiology*; D002478:Cells, Cultured; D002851:Chromatography, High Pressure Liquid; D002852:Chromatography, Ion Exchange; D015180:Electrophoresis, Gel, Two-Dimensional; D004730:Endothelium, Vascular / Q000166:cytology; D004926:Escherichia coli / Q000378:metabolism; D019143:Evolution, Molecular; D034482:Heterogeneous-Nuclear Ribonucleoprotein Group C / Q000378:metabolism*; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D047468:Immunoprecipitation; D007211:Indoles / Q000494:pharmacology; D007700:Kinetics; D008099:Liver / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D010696:Phloroglucinol / Q000031:analogs & derivatives* / Q000494:pharmacology; D010766:Phosphorylation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012313:RNA / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D012694:Serine / Q000737:chemistry; D013050:Spectrometry, Fluorescence
D034482:Heterogeneous-Nuclear Ribonucleoprotein Group C; C411652:IC 261; D007211:Indoles; D012333:RNA, Messenger; D012694:Serine; D012313:RNA; D006861:Hydrogen Peroxide; D010696:Phloroglucinol; D048128:Casein Kinase Ialpha