C. elegans cells showing H3K27me labellingLAURA GAYDOSAfter DNA replication and division, cells generally remember which of their genes should be active and which repressed—but how? A study in worms published today (September 18) in Science reveals that part of the mechanism involves divvying up modified histones—molecular tags that label active or repressed genes—between daughter chromosomes at replication. Researchers from the University of California, Santa Cruz and Indiana University, Bloomington, found that although the tags in each chromosome are reduced as a result of division, subsequent recruitment of histone-modifying enzymes reestablishes the full tag quota, thus preserving the memory of modifications for the next round of division.
“They show very elegantly using their system that modified histones can be inherited through multiple rounds of cell division and can be passed on . . . to the next generation,” said Shiv Grewal, an epigenetics and chromatin researcher at the National Cancer Institute who was not involved in the work. “That’s quite remarkable.”
Histones, the proteins around which DNA is wrapped to form chromatin, can be modified by the addition a various moieties. And such modifications are thought to represent—and even influence—the transcriptional activity of associated genes. Although the presence of these modifications at given genomic locations can be inherited from a parent cell to its daughters, exactly how this landscape of histone modifications is reestablished after DNA replication—when the histones are temporarily evicted ...
