In Science this week, a team led by Robert Martienssen from Cold Spring Harbor Laboratory and Institut de Biologie de l’École Normale Supérieure report on the discovery of how histone marks are preserved on heterochromatin in order to conserve parental gene expression programs in daughter cells. Using Arabidopsis, they showed that histone marks are kept intact by interactions between the enzyme ATXR5, which modifies histones, and a histone variant known as H3.1. The findings, the researchers say, demonstrate how histone variants can control epigenetic changes in gene expression by controlling the enzymes that reshape heterochromatin within a cell's nucleus.
Also in Science, a Harvard Medical School group publishes a new strategy for the self-assembly of DNA polyhedra that are bigger than previously produced structures. The researchers used a stiff three arm-junction DNA origami tile motif with precisely controlled angles and arm lengths to construct a tetrahedron, a triangular prism, a cube, a pentagonal prism, and a hexagonal prism with edge widths of 100 nanometers. The structures were visualized by transmission electron microscopy and by three-dimensional DNA-PAINT super-resolution fluorescent microscopy of single molecules in solution.