Studies on Heterogeniety of General Transcription Factor TFIID

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The core promoter of the mouse myelin basic protein (MBP) gene from -36 to +12 was tissue-specifically (brain) transcribed. Biochemical studies demonstrated that TFIID fraction contains factors involved in such a specific transcription. Tnus. we hypothesized the existence of a tissuespecific TFIID. We isolated a cDNA clone for TFIID from the mouse brain, and compared its structure with the human TFIID. Few minor differences were observed only in the N-terminal portion of the mouse TFIID. The C-terminus that is required for the TFIID function was identical among two TFIIDs. Only a single TFIID gene was detected in mouse genome. Northern blot analysis demonstated that the TFIID transcript is expressedas the same size RNAs in mouse tissues. Mutation analysis within the MBP core promoter showed that the TATA-box is not essential but TATA-flanking sequences were important for tissue-specific transcription. From these results, there may be no tissue-specific TFIID. In these days, TFIID associating factors (TAF) have been identified by other groups. In our case, it is suggested that a tissue-specific TAF can be involved in the core promoter-mediated tissue-specific transcription.