Physical mapping at 6q27 of the locus for the TATA box-binding protein, the DNA-binding subunit of TFIID and a component of SL1 and TFIIIB, strongly suggests that it is single copy in the human genome.
The TATA box-binding protein (TBP) has a fundamental role in eukaryotic cell metabolism, since it is necessary for transcription of class I, class II, and class III genes; in fact, TBP is the DNA-binding subunit of TFIID and a component of SL1 and TFIIIB. Contrary to the previously hypothesized existence of a family of genes coding for DNA-binding proteins highly related to TBP, our experiments show that the segment coding for the evolutionarily well-conserved carboxyl-terminal domain, involved in DNA binding, is unique; accordingly, we conclude that the TBP locus itself, which we have localized to 6q27, is single copy in the human genome. On the other hand, a cDNA fragment coding for the evolutionarily variable amino-terminal domain detects multiple cross-hybridizing sequences in the genome of higher eukaryotes. We suggest that the common motif is represented by the long string of glutamine codons, which characterizes the amino-terminal segment of human TBP: in fact, other proteins involved in transcription, such as TAF II 110, Sp1, and some homeobox proteins, are known to contain glutamine-rich segments.
Istituto di Biologia generale, Università di Catania, Italy.
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Motta
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Grzeschik
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D000818:Animals; D005075:Biological Evolution; D002874:Chromosome Mapping; D002896:Chromosomes, Human, Pair 6; D004268:DNA-Binding Proteins / Q000235:genetics*; D015894:Genome, Human; D006801:Humans; D006822:Hybrid Cells; D017404:In Situ Hybridization, Fluorescence; D035463:Pol1 Transcription Initiation Complex Proteins; D035181:TATA-Box Binding Protein; D035362:Transcription Factor TFIID; D035361:Transcription Factor TFIIIB; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics*
D004268:DNA-Binding Proteins; D035463:Pol1 Transcription Initiation Complex Proteins; D035181:TATA-Box Binding Protein; D035362:Transcription Factor TFIID; D035361:Transcription Factor TFIIIB; D014157:Transcription Factors; C063660:transcription initiation factor TIF-IB