title: Polycomb purification by in vivo biotinylation tagging reveals cohesin and Trithorax group proteins as interaction partners.
abstract: The maintenance of specific gene expression patterns during cellular proliferation is crucial for the identity of every cell type and the development of tissues in multicellular organisms. Such a cellular memory function is conveyed by the complex interplay of the Polycomb and Trithorax groups of proteins (PcG/TrxG). These proteins exert their function at the level of chromatin by establishing and maintaining repressed (PcG) and active (TrxG) chromatin domains. Past studies indicated that a core PcG protein complex is potentially associated with cell type or even cell stage-specific sets of accessory proteins. In order to better understand the dynamic aspects underlying PcG composition and function we have established an inducible version of the biotinylation tagging approach to purify Polycomb and associated factors from Drosophila embryos. This system enabled fast and efficient isolation of Polycomb containing complexes under near physiological conditions, thereby preserving substoichiometric interactions. Novel interacting proteins were identified by highly sensitive mass spectrometric analysis. We found many TrxG related proteins, suggesting a previously unrecognized extent of molecular interaction of the two counteracting chromatin regulatory protein groups. Furthermore, our analysis revealed an association of PcG protein complexes with the cohesin complex and showed that Polycomb-dependent silencing of a transgenic reporter depends on cohesin function.
authors.affiliation: Department of Biosystems Science and Engineering, Swiss Federal Institute of Technology Zürich, Mattenstrasse 26, 4058 Basel, Switzerland.
authors.forename: Gero
authors.initials: G
authors.lastname: Strübbe
authors.forename: Christian
authors.initials: C
authors.lastname: Popp
authors.forename: Alexander
authors.initials: A
authors.lastname: Schmidt
authors.forename: Andrea
authors.initials: A
authors.lastname: Pauli
authors.forename: Leonie
authors.initials: L
authors.lastname: Ringrose
authors.forename: Christian
authors.initials: C
authors.lastname: Beisel
authors.forename: Renato
authors.initials: R
authors.lastname: Paro
mesh_terms: D000818:Animals; D019921:Biotinylation; D018797:Cell Cycle Proteins / Q000378:metabolism*; D002843:Chromatin / Q000378:metabolism; D002850:Chromatography, Gel; D002868:Chromosomal Proteins, Non-Histone / Q000378:metabolism*; D004330:Drosophila / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D029721:Drosophila Proteins / Q000302:isolation & purification* / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000502:physiology*; D008024:Ligands; D013058:Mass Spectrometry; D009841:Oligonucleotides / Q000235:genetics; D063150:Polycomb Repressive Complex 1; D013053:Spectrophotometry; D000097722:Cohesins
chemical_list: D018797:Cell Cycle Proteins; D002843:Chromatin; D002868:Chromosomal Proteins, Non-Histone; D029721:Drosophila Proteins; D008024:Ligands; D009841:Oligonucleotides; D063150:Polycomb Repressive Complex 1; D000097722:Cohesins; C066770:Pc protein, Drosophila; C512571:trx protein, Drosophila