The δ Isoform of Protein Phosphatase Type 1 Is Localized in Nucleolus and Dephosphorylates Nucleolar Phosphoproteins
作者： Hirokazu Kotani , Masaaki Ito , Tetsuya Hamaguchi , Kazuhito Ichikawa , Takeshi Nakano
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摘要: Abstract The immunolocalization and substrates of protein phosphatases present in nucleolus were investigated using Swiss 3T3 cells Novikoff hepatoma ascites cells. phosphatase activity was detected the extract isolated nucleoli its inhibited by okadaic acid with IC50 value 160 nM. Immunoblotting assay indicated that PP1cδ but not PP1cα, PP1cγ1, PP2Ac localized nucleoli. Confocal microscopy showed nucleoli, nuclei, cytosol, though intensity fluorescence at stronger than cytosol or nuclei. co-localized major nucleolar phosphoprotein B23 capable dephosphorylating several proteins nucleolus, including B23. Km PP1 for recombinant B23.1, phosphorylated endogenous kinase(s), 3.5 μM. These results indicate is serine/threonine it dephosphorylates phosphoproteins,
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