Regulation of gene expression involves long-distance communication between 
regulatory elements and target promoters, but how this is achieved remains 
unknown. Insulator elements have been proposed to modulate the communication 
between regulatory elements and promoters due to their ability to insulate genes 
from regulatory elements or to take part in long-distance interactions. Using a 
high-resolution chromatin conformation capture (H3C) method, we show that the 
Drosophila gypsy insulator behaves as a conformational chromatin border that is 
able to prohibit contacts between a Polycomb response element (PRE) and a distal 
promoter. On the other hand, two spaced gypsy elements form a chromatin loop 
that is able to bring an upstream PRE in contact with a downstream gene to 
mediate its repression. Chromatin immunoprecipitation (ChIP) profiles of the 
Polycomb protein and its associated H3K27me3 histone mark reflect this 
insulator-dependent chromatin conformation, suggesting that Polycomb action at a 
distance can be organized by local chromatin topology.