Analysis of Groucho-histone interactions suggests mechanistic similarities between Groucho- and Tup1-mediated repression.
The Drosophila Groucho (Gro) protein is the defining member of a family of metazoan corepressors that have roles in many aspects of development, including segmentation, dorsal/ventral pattern formation, Notch signaling, and Wnt/Wg signaling. Previous speculation has suggested that Gro may be orthologous to the yeast corepressor Tup1. In support of this idea, a detailed alignment between the C-terminal WD-repeat domains of these two proteins shows that each Gro WD repeat is most similar to the Tup1 WD repeat occupying the corresponding position in that protein. Our analysis of Gro-histone interactions provides further support for a close evolutionary relationship between Gro and Tup1. In particular, we show that, as with the N-terminal region of Tup1, the N-terminal region of Gro is necessary and sufficient for direct binding to histones. The highest affinity interaction is with histone H3 and binding is primarily observed with hypoacetylated histones. Using transient transfection assays, we show that a Gal4-Gro fusion protein containing the histone-binding domain is able to repress transcription. Deletions that weaken histone binding also weaken repression. These findings, along with our recent report that Gro interacts with the histone deacetylase Rpd3, suggest a mechanism for Gro-mediated repression.
Flores-Saaib
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Department of Chemistry and Biochemistry, 5034 Young Hall, University of California, Los Angeles, 405 Hilgard Avenue, Los Angeles, CA 90095, USA.
Courey
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AJ
D000107:Acetylation; D000595:Amino Acid Sequence; D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015536:Down-Regulation; D004331:Drosophila melanogaster; D005656:Fungal Proteins / Q000737:chemistry / Q000378:metabolism*; D006655:Histone Deacetylases / Q000378:metabolism; D006657:Histones / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D009687:Nuclear Proteins; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D020449:Repetitive Sequences, Amino Acid; D012097:Repressor Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D016415:Sequence Alignment; D017384:Sequence Deletion / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D012984:Software; D014162:Transfection
D051792:Basic Helix-Loop-Helix Proteins; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D006655:Histone Deacetylases; D006657:Histones; D009687:Nuclear Proteins; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; C066502:TUP1 protein, S cerevisiae; C091023:gro protein, Drosophila