A conserved structural motif reveals the essential transcriptional repression function of Spen proteins and their role in developmental signaling.
Spen proteins regulate the expression of key transcriptional effectors in diverse signaling pathways. They are large proteins characterized by N-terminal RNA-binding motifs and a highly conserved C-terminal SPOC domain. The specific biological role of the SPOC domain (Spen paralog and ortholog C-terminal domain), and hence, the common function of Spen proteins, has been unclear to date. The Spen protein, SHARP (SMRT/HDAC1-associated repressor protein), was identified as a component of transcriptional repression complexes in both nuclear receptor and Notch/RBP-Jkappa signaling pathways. We have determined the 1.8 A crystal structure of the SPOC domain from SHARP. This structure shows that essentially all of the conserved surface residues map to a positively charged patch. Structure-based mutational analysis indicates that this conserved region is responsible for the interaction between SHARP and the universal transcriptional corepressor SMRT/NCoR (silencing mediator for retinoid and thyroid receptors/nuclear receptor corepressor. We demonstrate that this interaction involves a highly conserved acidic motif at the C terminus of SMRT/NCoR. These findings suggest that the conserved function of the SPOC domain is to mediate interaction with SMRT/NCoR corepressors, and that Spen proteins play an essential role in the repression complex.
Ariyoshi
Mariko
M
Medical Research Council, Laboratory of Molecular Biology, Cambridge CB2 2QH, UK.
Schwabe
John W R
JW
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D001667:Binding, Competitive; D017173:Caenorhabditis elegans; D002467:Cell Nucleus / Q000378:metabolism; D002474:Cell-Free System; D017124:Conserved Sequence; D018360:Crystallography, X-Ray; D004252:DNA Mutational Analysis; D004268:DNA-Binding Proteins; D004330:Drosophila; D029721:Drosophila Proteins; D018507:Gene Expression Regulation, Developmental; D005982:Glutathione Transferase / Q000378:metabolism; D056284:Histone Deacetylase 1; D006655:Histone Deacetylases / Q000378:metabolism; D018398:Homeodomain Proteins / Q000737:chemistry* / Q000378:metabolism* / Q000502:physiology*; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D009687:Nuclear Proteins / Q000737:chemistry* / Q000378:metabolism* / Q000502:physiology*; D010455:Peptides / Q000737:chemistry; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D016601:RNA-Binding Proteins; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D014158:Transcription, Genetic
D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D018398:Homeodomain Proteins; D009687:Nuclear Proteins; D010455:Peptides; D016601:RNA-Binding Proteins; C476510:SPEN protein, human; C402387:Spen protein, Drosophila; D005982:Glutathione Transferase; C110550:HDAC1 protein, human; D056284:Histone Deacetylase 1; D006655:Histone Deacetylases