Insulators, not Polycomb response elements, are required for long-range interactions between Polycomb targets in Drosophila melanogaster.
The genomic binding sites of Polycomb group (PcG) complexes have been found to cluster, forming Polycomb "bodies" or foci in mammalian or fly nuclei. These associations are thought to be driven by interactions between PcG complexes and result in enhanced repression. Here, we show that a Polycomb response element (PRE) with strong PcG binding and repressive activity cannot mediate trans interactions. In the case of the two best-studied interacting PcG targets in Drosophila, the Mcp and the Fab-7 regulatory elements, we find that these associations are not dependent on or caused by the Polycomb response elements they contain. Using functional assays and physical colocalization by in vivo fluorescence imaging or chromosome conformation capture (3C) methods, we show that the interactions between remote copies of Mcp or Fab-7 elements are dependent on the insulator activities present in these elements and not on their PREs. We conclude that insulator binding proteins rather than PcG complexes are likely to be the major determinants of the long-range higher-order organization of PcG targets in the nucleus.
Rutgers University, Department of Molecular Biology and Biochemistry, Piscataway, NJ 08854, USA.
Hua-Bing
HB
Li
Martin
M
Müller
Ilham Anne
IA
Bahechar
Olga
O
Kyrchanova
Katsuhito
K
Ohno
Pavel
P
Georgiev
Vincenzo
V
Pirrotta
D000818:Animals; D030801:Animals, Genetically Modified; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism; D017931:DNA Primers / Q000235:genetics; D029721:Drosophila Proteins / Q000235:genetics* / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000235:genetics* / Q000378:metabolism*; D004843:Epistasis, Genetic; D005127:Eye Color / Q000235:genetics; D017344:Genes, Insect; D038101:Insulator Elements; D010641:Phenotype; D063150:Polycomb Repressive Complex 1; D020218:Response Elements; D037941:Silencer Elements, Transcriptional
D017931:DNA Primers; D029721:Drosophila Proteins; C066770:Pc protein, Drosophila; D063150:Polycomb Repressive Complex 1