Novel nuclear shuttle proteins, HDBP1 and HDBP2, bind to neuronal cell-specific cis-regulatory element in the promoter for the human Huntington's disease gene.
Huntington's disease (HD) is a neurodegenerative disease caused by a CAG repeat expansion in exon 1 of the HD gene, and the expression level of either normal or mutant huntingtin is implicated in the pathogenesis of HD. However, a molecular base of the HD gene transcription has not been elucidated as yet. In this study, we identified two proteins, HDBP1 and HDBP2, which bind to the promoter region for the HD gene using a yeast one-hybrid system. Amino acid sequence analysis of the proteins deduced the presence of nuclear localization signal, nuclear export signal, zinc finger, serine/proline-rich region, and highly conserved C-terminal region. In vitro DNA binding assay indicated that the C-terminal conserved regions of the proteins were responsible for binding to the unique promoter DNA sequences of the HD gene. The DNA sequence protected from DNase I digestion was a 7-bp consensus sequence (GCCGGCG), which resides in triplicate at intervals of 13 bp within and proximal to the 20-bp direct repeat sequences of the HD promoter region. The mutation of 7-bp consensus sequence abolishes the HD promoter function in a neuronal cell line (IMR32). In human cultured cells, ectopically expressed green fluorescent protein-fused HDBP1 and HDBP2 localized in the cytoplasm, but both proteins totally shift from cytoplasm to nucleus by the treatment with an inhibitor of the nuclear export, leptomycin B, and mutagenesis of the putative nuclear export signals. Taken together, HDBP1 and HDBP2 are novel transcription factors shuttling between nucleus and cytoplasm and bind to the specific GCCGGCG, which is an essential cis-element for HD gene expression in neuronal cells.
Tanaka
Kazunori
K
Department of Molecular Neuroscience, Institute of Medical Sciences, Tokai University, Isehara, Kanagawa 259-1193, Japan.
Shouguchi-Miyata
Junko
J
Miyamoto
Natsuki
N
Ikeda
Joh-E
JE
D000595:Amino Acid Sequence; D015152:Blotting, Northern; D002460:Cell Line; D017124:Conserved Sequence; D003593:Cytoplasm / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D003850:Deoxyribonuclease I / Q000378:metabolism; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology; D015723:Gene Library; D017930:Genes, Reporter; D049452:Green Fluorescent Proteins; D006367:HeLa Cells; D006801:Humans; D000071058:Huntingtin Protein; D008156:Luciferases / Q000378:metabolism; D008164:Luminescent Proteins / Q000378:metabolism; D008957:Models, Genetic; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000737:chemistry* / Q000235:genetics*; D009474:Neurons / Q000378:metabolism*; D019913:Nuclear Localization Signals; D009687:Nuclear Proteins / Q000737:chemistry* / Q000235:genetics*; D010957:Plasmids / Q000378:metabolism; D011392:Proline / Q000737:chemistry; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D012694:Serine / Q000737:chemistry; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*; D014158:Transcription, Genetic; D020798:Two-Hybrid System Techniques; D016335:Zinc Fingers
D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D005231:Fatty Acids, Unsaturated; C086055:HTT protein, human; D000071058:Huntingtin Protein; D008164:Luminescent Proteins; D009419:Nerve Tissue Proteins; D019913:Nuclear Localization Signals; D009687:Nuclear Proteins; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; C480633:SLC2A4RG protein, human; D014157:Transcription Factors; C484332:ZNF395 protein, human; D049452:Green Fluorescent Proteins; D012694:Serine; D011392:Proline; D008156:Luciferases; D003850:Deoxyribonuclease I; C038753:leptomycin B