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Mediators of activation of fushi tarazu gene transcription by BmFTZ-F1.

1994; Taylor & Francis; Volume: 14; Issue: 5 Linguagem: Inglês

10.1128/mcb.14.5.3013

1098-5549

F Q Li, Hitoshi Ueda, Susumu Hirose,

RNA Research and Splicing

Transcriptional activation by many eukaryotic sequence-specific regulators appears to be mediated through transcription factors which do not directly bind to DNA. BmFTZ-F1 is a silkworm counterpart of FTZ-F1, a sequence-specific activator of the fushi tarazu gene in Drosophila melanogaster. We report here the isolation of 18- and 22-kDa polypeptides termed MBF1 and MBF2, respectively, that form a heterodimer and mediate activation of in vitro transcription from the fushi tarazu promoter by BmFTZ-F1. Neither MBF1, MBF2, nor a combination of them binds to DNA. MBF1 interacts with BmFTZ-F1 and stabilizes the BmFTZ-F1-DNA complex. MBF1 also makes direct contact with TATA-binding protein (TBP). Both MBF1 and MBF2 are necessary to form a complex between BmFTZ-F1 and TBP. We propose a model in which MBF1 and MBF2 form a bridge between BmFTZ-F1 and TBP and mediate transactivation by stabilizing the protein-DNA interactions.