Fabien Sassolas

Evolution of sequence-mediated nucleosome positioning in eukaryotes

The nucleosome is a complex of histones and ~150 bp of DNA. It is a major constituent of chromatin in eukaryotes, covering 75–90% of genomes. Our team has developed a physical model based on the elastic properties of the DNA sequence (Vaillant et al. 2007). This model predicts Nucleosome Inhibitory Energy Barriers (NIEBs), at the border of which nucleosomes are positionned through statistical positioning (Kornberg & Stryer 1988). Here, we report that NIEBs can be predicted across eukaryotes and are functional, i.e they position nucleosomes in every eukaryotic species tested (from human to Trypanosoma brucei). We report that NIEBs affect local sequence evolution in a strikingly similar manner across eukaryotes. Their evolution is also affected by microsatellites and transposable elements (SINE and LINEs). Finally, some level of association with TSS and TTS is reported, hinting at one possible biological function, even though a lot of work remain to be done on this subject.