第1097回生物科学セミナー
Molecular co-evolution of genomes and chromatin
Daniel Zilberman（UC Berkeley）
2016年05月18日(水) 17:00-18:00 理学部2号館 講堂
The Dnmt1 DNA methyltransferase epigenetically propagates symmetrical CG methylation in many eukaryotes, including flowering plants and vertebrates. Their genomes are typically depleted of CG dinucleotides, because of imperfect repair of deaminated methylcytosines. We extensively surveyed diverse species lacking Dnmt1 and show that, surprisingly, symmetrical CG methylation is nonetheless requently present, catalyzed by a novel DNA methyltransferase family, Dnmt5. Numerous Dnmt5-containing organisms that diverged over a billion years ago exhibit clustered methylation specifically in nucleosome linkers. Clustered methylation occurs at unprecedented densities and directly disfavors nucleosomes, contributing to nucleosome positioning between clusters. Dense methylation is enabled by a novel regime of genomic sequence evolution that enriches CG dinucleotides, driving the highest CG frequencies known. We propose that species with dense linker methylation experience genome-wide epigenetic inheritance of nucleosome positions, which provides the selective pressure to maintain the CG-enriching mutational process that enables dense methylation.
参考文献: Huff & Zilberman (2014) Cell 156, 1286-
