Abstract
Polycomb group (PcG) protein complexes repress transcription by modifying target gene chromatin. In Drosophila, this repression requires association of PcG protein complexes with cis-regulatory Polycomb response elements (PREs), but the interactions permitting formation of these assemblies are poorly understood. We show that the Sfmbt subunit of the DNA-binding Pho-repressive complex (PhoRC) and the Scm subunit of the canonical Polycomb-repressive complex 1 (PRC1) directly bind each other through their SAM domains. The 1.9 Å crystal structure of the Scm-SAM:Sfmbt-SAM complex reveals the recognition mechanism and shows that Sfmbt-SAM lacks the polymerization capacity of the SAM domains of Scm and its PRC1 partner subunit, Ph. Functional analyses in Drosophila demonstrate that Sfmbt-SAM and Scm-SAM are essential for repression and that PhoRC DNA binding is critical to initiate PRC1 association with PREs. Together, this suggests that PRE-tethered Sfmbt-SAM nucleates PRC1 recruitment and that Scm-SAM/Ph-SAM-mediated polymerization then results in the formation of PRC1-compacted chromatin.
| Original language | English |
|---|---|
| Journal | Genes & Development |
| Volume | 30 |
| Issue number | 9 |
| Pages (from-to) | 1116-27 |
| Number of pages | 12 |
| ISSN | 0890-9369 |
| DOIs | |
| Publication status | Published - 1 May 2016 |
| Externally published | Yes |
Keywords
- Animals
- Chromatin
- Crystallography
- Drosophila Proteins
- Drosophila melanogaster
- Gene Expression Regulation
- Models, Molecular
- Polycomb Repressive Complex 1
- Polycomb-Group Proteins
- Polymerization
- Protein Binding
- Protein Structure, Tertiary
- Response Elements
- Journal Article