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Mol. Cell. Biol., 12 1995, 6923-6931, Vol 15, No. 12
SR Dawson, DL Turner, H Weintraub and SM Parkhurst
The Hairy/Enhancer of split/Deadpan family of basic helix-loop-helix (bHLH)
proteins function as transcriptional repressors. We have examined the
mechanisms of repression used by the Hairy and E(SPL) proteins by assaying
the antagonism between wild-type or altered Hairy/E(SPL) and Scute bHLH
proteins during sex determination in Drosophila melanogaster. Domain
swapping and mutagenesis of the Hairy and E(SPL) proteins show that three
evolutionarily conserved domains are required for their function: the bHLH,
Orange, and WRPW domains. However, the suppression of Scute activity by
Hairy does not require the WRPW domain. We show that the Orange domain is
an important functional domain that confers specificity among members of
the Hairy/E(SPL) family. In addition, we show that a Xenopus Hairy homology
conserves not only Hairy's structure but also its biological activity in
our assays. We propose that transcriptional repression by the Hairy/E(SPL)
family of bHLH proteins involves two separable mechanisms: repression of
specific transcriptional activators, such as Scute, through the bHLH and
Orange domains and repression of other activators via interaction of the
C-terminal WRPW motif with corepressors, such as the Groucho protein.
Copyright © 1995, American Society for Microbiology
Specificity for the hairy/enhancer of split basic helix-loop-helix (bHLH) proteins maps outside the bHLH domain and suggests two separable modes of transcriptional repression
Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington 98104, USA.
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