A composite nuclear export signal in the TBP-associated factor TAFII105.
TAF(II)105 is a sub-stoichiometric subunit of TFIID important for activation of anti-apoptotic genes and B cell specific genes by the transcription factors NF-kappaB and OCA-B. This subunit is highly enriched in B and T lymphocytes, and its expression is regulated at a posttranscriptional level. In the present study we investigated the subcellular localization of TAF(II)105. In normal B cells, a significant portion of native TAF(II)105 protein is found in the cytoplasm. Treatment of these cells with B cell-specific stimuli decreased the level of cytoplasmic TAF(II)105. In adherent cultured cells, TAF(II)105 is predominantly nuclear; however, a small fraction of the cells showed either cytoplasmic or homogenous distribution of TAF(II)105. Analysis of different TAF(II)105 mutants and green fluorescence protein fusion proteins identified a region composed of two adjacent sequences displaying nuclear export activity, suggesting that nuclear export of TAF(II)105 is mediated by a composite nuclear export signal. TAF(II)105 nuclear export signal is leptomycin B-resistant indicating that it belongs to a CRM1-independent nuclear export pathway. These results reveal a novel mode of regulation of a specialized component of the general transcription apparatus that may affect the transcription of its target genes.
Rashevsky-Finkel
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Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot 76100, Israel.
Silkov
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Dikstein
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R
D021581:Active Transport, Cell Nucleus; D000595:Amino Acid Sequence; D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology; D017209:Apoptosis; D001402:B-Lymphocytes / Q000378:metabolism; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism*; D002478:Cells, Cultured; D003593:Cytoplasm / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology; D005347:Fibroblasts / Q000378:metabolism; D049452:Green Fluorescent Proteins; D006801:Humans; D007668:Kidney / Q000378:metabolism; D008164:Luminescent Proteins / Q000378:metabolism; D051379:Mice; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D019913:Nuclear Localization Signals; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013154:Spleen / Q000166:cytology; D035381:TATA-Binding Protein Associated Factors; D013997:Time Factors; D035362:Transcription Factor TFIID; D014157:Transcription Factors / Q000737:chemistry* / Q000378:metabolism*; D014158:Transcription, Genetic; D014162:Transfection
D000903:Antibiotics, Antineoplastic; D004268:DNA-Binding Proteins; D005231:Fatty Acids, Unsaturated; D008164:Luminescent Proteins; D019913:Nuclear Localization Signals; D011993:Recombinant Fusion Proteins; C101881:TAF4B protein, human; D035381:TATA-Binding Protein Associated Factors; C491103:Taf4b protein, mouse; D035362:Transcription Factor TFIID; D014157:Transcription Factors; D049452:Green Fluorescent Proteins; C038753:leptomycin B