A new model for long-range chromatin reorganisation linked to enhancer activation [ChIP-chip]

The most prominent model for long-range enhancer regulation involves direct enhancer-promoter interaction by looping out the intervening chromatin. Using a synthetic biology approach, we have determined that a chromatin unfolding between Shh and its enhancers is regulated specifically by the Shh-Brain-Enhancers and is mediated by the recruitment of Poly (ADP-Ribose) Polymerase 1. This ‘chromatin unfolding’ model represents a new mechanism of long-range enhancer-promoter communication in addition to the looping and tracking models. ChIP-on-chip for H3K27me3 and H3K27ac on the Shh regulatory region on ESCs and transfected ESCs showed a gain of H3k27ac specifically on active enhancers and no loss of Polycomb marks upon Shh activation. Comparison of different Tale-Vp64 transfected ESCs. Tiling ChIP-chip for H3K27me3 and H3K27ac profiles across Shh and other candidate gene loci.