Section: New Results

Exploring the evolution of chromatin-associated proteins

participants: A Crombach

Eukaryotic gene regulation depends strongly on chromatin state. High-throughput studies in the fruit fly Drosophila melanogaster have shown that instead of the canonical two types of chromatin, hetero- and euchromatin, one can subdivide chromatin into five states. These states are each characterized by a unique combination of chromatin-associated proteins (CAPs). We were interested in the evolution of CAPs and studied them by means of phylogenomic methods. We found three evolutionary trends. One type of heterochomatin, called GREEN, is specific to centromeres and some of its proteins are found to be under a Red Queen type evolution, where they rapidly accumulate amino acid changes. The second type of heterochromatin, BLUE, is tightly linked to Polycomb Group proteins. These proteins are important regulators in developmental processes and our findings confirm their origin in multicellular organisms. Finally, the two euchromatic types, YELLOW and RED, have strong lineage-specific characteristics. Their origins seem to date back to the start of eukaryotic life.