Casein kinase II phosphorylation regulates alphaNAC subcellular localization and transcriptional coactivating activity.
The subcellular localization of the alphaNAC coactivator is regulated, but the signaling pathways controlling its nucleocytoplasmic shuttling and coactivation function are not completely characterized. We report here that casein kinase II (CK2) phosphorylated alphaNAC on several phosphoacceptor sites, especially in an amino-terminal cluster. Deletion or mutation of the clustered CK2 sites induced nuclear accumulation of alphaNAC in cells. alphaNAC also localized to the nucleus when endogenous CK2 activity was inhibited by quercetin or 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB). These observations suggested that phosphorylation by CK2 might play a signaling role in the nuclear export of alphaNAC. Interestingly, inhibition of the chromosome region maintenance 1 (CRM1) exportin by leptomycin B (LMB) led to accumulation of alphaNAC in the nucleus. We conclude that CK2 phosphorylation of the N-terminal cluster corresponds to the signal for alphaNAC's nuclear export via a CRM1-dependent pathway. Finally, the nuclear accumulation of the protein resulting from the lack of CK2 phosphorylation mediated a slight but significant increase of the alphaNAC coactivating function on AP-1 transcriptional activity. Thus, alphaNAC's exit from the nucleus and capacity to potentiate transcription appear dependent on its phosphorylation status.
Quélo
Isabelle
I
Genetics Unit, Shriners Hospitalfor Children, Montreal (Quebec) Canada H3G 1A6.
Gauthier
Claude
C
St-Arnaud
René
R
D021581:Active Transport, Cell Nucleus; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D019556:COS Cells; D047390:Casein Kinase II / Q000378:metabolism / Q000502:physiology*; D002467:Cell Nucleus / Q000378:metabolism; D002522:Chlorocebus aethiops; D016000:Cluster Analysis; D003600:Cytosol / Q000378:metabolism; D004004:Dichlororibofuranosylbenzimidazole / Q000494:pharmacology; D000939:Epitopes / Q000737:chemistry; D005231:Fatty Acids, Unsaturated / Q000378:metabolism; D017353:Gene Deletion; D005786:Gene Expression Regulation; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D028884:Karyopherins / Q000378:metabolism; D008156:Luciferases / Q000378:metabolism; D008957:Models, Genetic; D018832:Molecular Chaperones; D008969:Molecular Sequence Data; D009154:Mutation; D010750:Phosphoproteins / Q000737:chemistry; D010766:Phosphorylation; D017354:Point Mutation; D017434:Protein Structure, Tertiary; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D013997:Time Factors; D015534:Trans-Activators / Q000096:biosynthesis / Q000502:physiology*; D018808:Transcription Factor AP-1 / Q000378:metabolism; D014158:Transcription, Genetic; D014162:Transfection; D000097606:Exportin 1 Protein
D047390:Casein Kinase II; D004004:Dichlororibofuranosylbenzimidazole; D000939:Epitopes; D005231:Fatty Acids, Unsaturated; D028884:Karyopherins; D008156:Luciferases; D018832:Molecular Chaperones; D010750:Phosphoproteins; D018160:Receptors, Cytoplasmic and Nuclear; D011994:Recombinant Proteins; D015534:Trans-Activators; D018808:Transcription Factor AP-1; D000097606:Exportin 1 Protein; C096099:nascent-polypeptide-associated complex; C038753:leptomycin B