Abstract
The RNA polymerase II and III human small nuclear RNA promoters have a common basal element, the proximal sequence element, which binds the TATA box-binding protein-containing complex SNAPc. They also contain an enhancer characterized by a highly conserved octamer sequence, which constitutes a binding site for the broadly expressed POU domain transcription factor Oct-1. The POU domain is a bipartite DNA-binding domain consisting of a POU-homeo (POUH) domain and a POU-specific (POUs) domain joined by a flexible linker. Here, we show that the Oct-1 POU domain but not the related Pit-1 POU domain can facilitate the binding of SNAPc to the proximal sequence element, and activate transcription. The effect is probably mediated by protein-protein contacts, and 1 of 30 amino acid differences between the Oct-1 and Pit-1 POUs domains is the key determinant for the differential interaction with SNAPc and the ability to activate transcription. These results show that a function that is the hallmark of activation domains, namely, recruitment of a basal transcription complex resulting in activation of transcription, can be performed by a DNA-binding domain. In this case, subtle changes between activator DNA-binding domains, as subtle as a single amino acid difference, can profoundly affect interaction with the basal transcription machinery.
Publication types
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Comparative Study
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Amino Acid Sequence
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Base Sequence
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Binding Sites
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Cloning, Molecular
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Conserved Sequence
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DNA-Binding Proteins / biosynthesis
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DNA-Binding Proteins / metabolism*
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Genes, Homeobox
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Glutathione Transferase / biosynthesis
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Glutathione Transferase / metabolism
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Homeodomain Proteins / biosynthesis
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Homeodomain Proteins / metabolism*
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Host Cell Factor C1
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Humans
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Molecular Sequence Data
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Mutagenesis, Site-Directed
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Octamer Transcription Factor-1
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Octamer Transcription Factor-2
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Oligonucleotide Probes
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Polymerase Chain Reaction
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Promoter Regions, Genetic
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RNA Polymerase I / metabolism
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RNA Polymerase II / metabolism
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RNA, Small Nuclear / biosynthesis*
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Recombinant Fusion Proteins / biosynthesis
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Recombinant Fusion Proteins / metabolism
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Sequence Homology, Amino Acid
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TATA Box
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TATA-Box Binding Protein
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Transcription Factor Pit-1
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Transcription Factors / biosynthesis
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Transcription Factors / metabolism*
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Transcription, Genetic*
Substances
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DNA-Binding Proteins
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HCFC1 protein, human
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Homeodomain Proteins
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Host Cell Factor C1
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Octamer Transcription Factor-1
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Octamer Transcription Factor-2
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Oligonucleotide Probes
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POU1F1 protein, human
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POU2F1 protein, human
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POU2F2 protein, human
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RNA, Small Nuclear
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Recombinant Fusion Proteins
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TATA-Box Binding Protein
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Transcription Factor Pit-1
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Transcription Factors
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Glutathione Transferase
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RNA Polymerase II
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RNA Polymerase I