The new research shows that, although tightly packed, heterochromatin is perhaps less dense than previously thought. Made up of nucleosomes–roll-shaped bundles of DNA and protein–the heterochromatin is connected by a velcro-like feature called “Heterochromatin Protein 1 (HP1).” This fundamental feature allows the body to “lock down” genes so they cannot be transcribed.
“Life as we know it relies on these principles,” said Matthias Wolf, one of the leading authors of the paper and head of the Molecular Cryo-Electron Microscopy Unit at the Okinawa Institute of Science and Technology, Graduate University (OIST).
“This work is an example of a very fruitful collaboration, which would not have been possible by any of the research groups alone,” said Hitoshi Kurumizaka, the leading author of the study at Waseda University. There, along with Shinichi Machida, an assistant professor at Waseda and co-first author on the paper, researchers successfully purified heterochromatin in vitro. Researchers at OIST imaged these samples in glass-like amorphous ice, which contains hundreds of pieces of heterochromatin, under a cryo-electron microscope.