Nuclear localization of basonuclin in human keratinocytes and the role of phosphorylation.
Basonuclin is a zinc-finger protein found in basal cells of the epidermis. In human keratinocyte cultures, basonuclin is susceptible to serine-phosphorylation and the addition of the phosphatase inhibitor, okadaic acid, promotes accumulation of basonuclin in the cytoplasm. The region of basonuclin containing the nuclear localization signal of basonuclin is necessary for nuclear localization of the protein and Ser-541, located immediately C-terminal to the nuclear localization signal, is the principal phosphorylation site in vitro. A nearly complete basonuclin transiently expressed in cultured keratinocytes localizes predominantly in the nucleus, but substitution of aspartic acid for Ser-541 promotes cytoplasmic localization. The same substitution of Ser-537 has a similar but weaker effect. Substitution of both serine residues by alanine leads to nuclear localization. These results show that nuclear localization of basonuclin depends on serine dephosphorylation, primarily of Ser-541. Different subcellular locations of basonuclin in different keratinocyte subtypes are therefore most likely to be controlled by the state of phosphorylation of Ser-541.
Iuchi
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Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston MA 02115, USA.
Green
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D016475:3T3 Cells; D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D004268:DNA-Binding Proteins; D006801:Humans; D015603:Keratinocytes / Q000378:metabolism*; D051379:Mice; D016296:Mutagenesis; D010750:Phosphoproteins; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D012694:Serine / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism; D014157:Transcription Factors; D014407:Tumor Cells, Cultured
C511595:Bnc1 protein, mouse; D004268:DNA-Binding Proteins; D010750:Phosphoproteins; D011506:Proteins; D014157:Transcription Factors; C077914:BNC1 protein, human; D012694:Serine