Comparative analysis of chromatin organization across three organisms 

ENCODE was launched in 2003 to decipher the different genomic elements present in the human genome. One of the goals of the massive endeavor was to understand the epigenetic role of gene expression regulation.

The project studied the effect of the structure of chromatin (DNA wrapped around histone proteins) on the degree to which genes are expressed.

In a Nature¹ letter, a large international consortium of 36 institutions, including the University of Alexandria, Egypt, present the first systematic catalogue of the differences in chromatin organization between the fly, worm and human, while also providing 800 additional data sets to the ENCODE database.

Changes in the structure of chromatin are a result of a complex combinatorial effect of different chemical modifications to histone proteins, resulting in the binding of other non-histone proteins. 

Fly and worm are commonly applied model systems to study this, but there are notable differences in chromatin organization between fly, worm and human, necessitating an understanding of these differences before conclusions drawn from studies on these models can be generalized.

The consortium used techniques that capture proteins bound to DNA in cells to find DNA elements where histones, modified histones, or non-histone proteins are bound. 

By carrying out these experiments on a genome-wide scale, and covering the landscape of all the different possible histone modifications, as well as a multitude of non-histone proteins, on cell lines from different developmental stages from the three organisms, they created comprehensive maps detailing similarities and differences in chromatin organization.

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