| Research Abstract |
Transcription initiation is the most important step of gene expression. The reaction of initiation is regulated by interactions between gene-specific transcription factors and basal transcription factors including RNA polymerase II.Basal transcription factors fromed the preinitiation complex (PIC). We analyzed function and structure of TFIIA,one of the basal transcription factors, and elucidated that TFIIA worked as a coactivator through bridging between activators and PIC.Human TFIIA is composed of three subunits with the molecular weights of 37kD,19kD,13kD.TFIIA has been thought to regulate basal transcription activity by binding to TFIID.We made recombinant TBP-fixed latex beads and purified human TFIIA from HeLa cell nuclear extracts by using the beads (Shiroya et al., Internl.J.Bio-chromatog., 1 : 191-198,1995). We determined partial amino acid sequences of the 37kD subunit and isolated its cDNA clone (Ma.et al., Genes Dev., 7 : 2246-2257,1993). We have showed that TFIIA released Dr2-mediated suppression of transcription and coactivated Ga14-VP16-mediated transcription activation. FTZ-F1 is an activator which stimulate expression of the fushi tarazu gene of Drosophila. BmFTZ-F1 is the silk-worm counterpart of FTZ-F1. Recently, MBF1 and MBF2 have been identified as coactivators of BmFTZ-F1. MBF1 has been shown to interact with both BmFTZ-F1 and TBP.We elucidatethat MBF2 interacts with both MBF1 and TFIIA (Li, F-Q., et al., submitted). This result confirms that TFIIA worked as a coactivator through bridging between activator and PIC.
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