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Biochem Biophys Res Commun. 1999 Dec 9;266(1):147-51.

MIDA1, an Id-associating protein, has two distinct DNA binding activities that are converted by the association with Id1: a novel function of Id protein.

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Institute of Development, Aging and Cancer, Tohoku University, 4-1 Seiryomachi, Aoba-ku, Sendai, 980-8575, Japan.


Id proteins not only regulate cell differentiation negatively, but they also promote growth, immortalization, and apoptosis. To know the mechanism of how Id regulates cell fate, we previously isolated an Id-associating protein, MIDA1, which positively regulates cell growth (1). Its predicted amino acid sequence consists of a Zuotin (a Z-DNA binding protein in yeast) homology region and tryptophan-mediated repeats (Tryp-med repeats). MIDA1 exhibits a sequence-specific DNA binding activity through the Tryp-med repeats (manuscript in preparation). In this study, we revealed that, like Zuotin, MIDA1 can specifically bind to Z-DNA. This suggested that MIDA is a novel DNA binding protein that has two different DNA binding activities. Furthermore, association of Id1 with MIDA1 stimulated the sequence-specific DNA binding activity, while it inhibited the Z-DNA binding activity. Therefore, we concluded that MIDA1 may act as a mediator of the growth-promoting function of Id, by switching the two DNA binding activities of MIDA1.

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