Trilogies of Histone Lysine Methylation as Epigenetic Landmarks of the Eukaryotic Genome

Abstract

The past several years have been highlighted by thelandmark descriptions of the genomes of several modelorganisms. The significance of these findings becomeseven greater following the nearly full sequence assemblyof the human genome. Together, these "genome projects"have shown that more complex eukaryotic model organisms have a much bigger genome than unicellular eukaryotes, although the increased "biocomplexity" is notreflected by an equivalent expansion in the number ofprotein-coding genes (e.g., ~40,000 in humans vs. ~6,000in Saccharomyces cerevisiae). These results stronglysuggest that biocomplexity is only in part regulated byoverall gene number, but largely depends on combinatorial control triggering a vast number of gene expressionpatterns. In addition, mechanisms other than DNA sequence information have been used during evolution tobetter index and regulate the complex developmental programs and key regulatory processes, such as chromosomesegregation and cell division of eukaryotic genomes...