PDBsum entry 5j8y

Nuclear protein

PDB id: 5j8y

Contents

Protein chains

78 a.a.

69 a.a.

Waters ×155

PDB id:

5j8y

Name:

Nuclear protein

Title:

Crystal structure of the scm-sam and sfmbt-sam heterodimer

Structure:

Polycomb protein scm. Chain: a, b. Fragment: unp residues 803-877. Synonym: sex comb on midleg protein. Engineered: yes. Mutation: yes. Polycomb protein sfmbt. Chain: c, d. Fragment: unp residues 1137-1220.

Source:

Drosophila melanogaster. Fruit fly. Organism_taxid: 7227. Gene: scm, cg9495. Expressed in: escherichia coli. Expression_system_taxid: 562. Gene: sfmbt, cg16975.

Resolution:

1.98Å R-factor: 0.256 R-free: 0.277

Authors:

F.Frey,C.Benda,J.Mueller

Key ref:

F.Frey et al. (2016). Molecular basis of PRC1 targeting to Polycomb response elements by PhoRC. Genes Dev, 30, 1116-1127. PubMed id: 27151979 DOI: 10.1101/gad.279141.116

Date:

08-Apr-16 Release date: 18-May-16

Protein chains

Q9VHA0  (SCM_DROME) -  Polycomb protein Scm from Drosophila melanogaster

Seq: 877 a.a.

Struc: 78 a.a.*

Protein chains

Q9VK33  (SMBT_DROME) -  Polycomb protein Sfmbt from Drosophila melanogaster

Seq: 1220 a.a.

Struc: 69 a.a.*

* PDB and UniProt seqs differ at 5 residue positions (black crosses)

DOI no: 10.1101/gad.279141.116

Genes Dev 30:1116-1127 (2016)

PubMed id: 27151979

Molecular basis of PRC1 targeting to Polycomb response elements by PhoRC.

F.Frey, T.Sheahan, K.Finkl, G.Stoehr, M.Mann, C.Benda, J.Müller.

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.