title: Structural basis for targeting the chromatin repressor Sfmbt to Polycomb response elements.
abstract: Polycomb group (PcG) protein complexes repress developmental regulator genes by modifying their chromatin. How different PcG proteins assemble into complexes and are recruited to their target genes is poorly understood. Here, we report the crystal structure of the core of the Drosophila PcG protein complex Pleiohomeotic (Pho)-repressive complex (PhoRC), which contains the Polycomb response element (PRE)-binding protein Pho and Sfmbt. The spacer region of Pho, separated from the DNA-binding domain by a long flexible linker, forms a tight complex with the four malignant brain tumor (4MBT) domain of Sfmbt. The highly conserved spacer region of the human Pho ortholog YY1 binds three of the four human 4MBT domain proteins in an analogous manner but with lower affinity. Comparison of the Drosophila Pho:Sfmbt and human YY1:MBTD1 complex structures provides a molecular explanation for the lower affinity of YY1 for human 4MBT domain proteins. Structure-guided mutations that disrupt the interaction between Pho and Sfmbt abolish formation of a ternary Sfmbt:Pho:DNA complex in vitro and repression of developmental regulator genes in Drosophila. PRE tethering of Sfmbt by Pho is therefore essential for Polycomb repression in Drosophila. Our results support a model where DNA tethering of Sfmbt by Pho and multivalent interactions of Sfmbt with histone modifications and other PcG proteins create a hub for PcG protein complex assembly at PREs.
authors.affiliation: European Molecular Biology Laboratory, 69117 Heidelberg, Germany.
authors.forename: Claudio
authors.initials: C
authors.lastname: Alfieri
authors.forename: Maria Cristina
authors.initials: MC
authors.lastname: Gambetta
authors.forename: Raquel
authors.initials: R
authors.lastname: Matos
authors.forename: Sebastian
authors.initials: S
authors.lastname: Glatt
authors.forename: Peter
authors.initials: P
authors.lastname: Sehr
authors.forename: Sven
authors.initials: S
authors.lastname: Fraterman
authors.forename: Matthias
authors.initials: M
authors.lastname: Wilm
authors.forename: Jürg
authors.initials: J
authors.lastname: Müller
authors.forename: Christoph W
authors.initials: CW
authors.lastname: Müller
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002868:Chromosomal Proteins, Non-Histone / Q000737:chemistry / Q000378:metabolism; D029721:Drosophila Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D004331:Drosophila melanogaster / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D063146:Polycomb-Group Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D055550:Protein Stability; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D050986:YY1 Transcription Factor / Q000737:chemistry / Q000378:metabolism
chemical_list: D002868:Chromosomal Proteins, Non-Histone; D029721:Drosophila Proteins; C546112:MBTD1 protein, human; D063146:Polycomb-Group Proteins; C542497:Sfmbt protein, Drosophila; D050986:YY1 Transcription Factor; C494698:YY1 protein, human; C113295:pho protein, Drosophila
keywords: Pho; PhoRC; Polycomb; Polycomb response element; Sfmbt; YY1