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Mol. Cell. Biol., 08 1997, 4820-4829, Vol 17, No. 8
W Hanna-Rose, JD Licht and U Hansen
To identify biologically functional regions in the product of the
Drosophila melanogaster gene Kruppel, we cloned the Kruppel homolog from
Drosophila virilis. Both the previously identified amino (N)- terminal
repression region and the DNA-binding region of the D. virilis Kruppel
protein are greater than 96% identical to those of the D. melanogaster
Kruppel protein, demonstrating a selective pressure to maintain the
integrity of each region during 60 million to 80 million years of
evolution. An additional region in the carboxyl (C) terminus of Kruppel
that was most highly conserved was examined further. A 42- amino-acid
stretch within the conserved C-terminal region also encoded a transferable
repression domain. The short, C-terminal repression region is a composite
of three subregions of distinct amino acid composition, each containing a
high proportion of either basic, proline, or acidic residues. Mutagenesis
experiments demonstrated, unexpectedly, that the acidic residues contribute
to repression function. Both the N-terminal and C-terminal repression
regions were tested for the ability to affect transcription mediated by a
variety of activator proteins. The N-terminal repression region was able to
inhibit transcription in the presence of multiple activators. However, the
C-terminal repression region inhibited transcription by only a subset of
the activator proteins. The different activator specificities of the two
regions suggest that they repress transcription by different mechanisms and
may play distinct biological roles during Drosophila development.
Copyright © 1997, American Society for Microbiology
Two evolutionarily conserved repression domains in the Drosophila Kruppel protein differ in activator specificity
Dana-Farber Cancer Institute and Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA.
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