Ash1p is a site-specific DNA-binding protein that actively represses transcription

ASH1 encodes a protein that is localized specifically to the daughter cell nucleus, where it has been proposed to repress transcription of the HO gene . Using Ash1p purified from baculovirus-infected insect cells, we have show n that Ash1p binds specific DNA sequences in the HO promoter, DNase I prote ction analyses showed that Ash1p recognizes a consensus sequence, YTGAT, Mu tation of this consensus abolishes Ash1p DNA binding in vitro. We have show n that Ash1p requires an intact zinc-binding domain in its C terminus for r epression of HO in vivo and that this domain may be involved in DNA binding . A heterologous DNA-binding domain fused to an N-terminal segment of Ash1p functions as an active repressor of transcription. Our studies indicate th at Ash1p is a DNA-binding protein of the GATA family with a separable trans criptional repression domain.