Notch and Delta are transmembrane proteins that allow neighbouring cells to communicate during development. Here, quantitative time-lapse microscopy has been used to show that the response of Notch to Delta on a neighbouring cell is graded, whereas its response to Delta on the same cell is sharp and occurs at a fixed threshold. A mathematical model explores how this new design principle enhances the sharpness of developmental boundaries set by classical lateral inhibition

Almost 200 million people worldwide are chronically infected with hepatitis C virus. Current treatments are poorly tolerated and not wholly effective, so new drugs are needed. Here, a potent new inhibitor of hepatitis C virus is described. This inhibitor targets the viral protein NS5A, and shows potential as part of a therapeutic regimen based on a combination of viral inhibitors

DNA methylation is an important epigenetic mark in many eukaryotes. In Arabidopsis plants, small interfering RNAs bound to the Argonaute 4 (AGO4) protein can direct de novo DNA methylation and consequent gene silencing. Here, a new regulator of RNA-directed DNA methylation has been discovered. This protein, RDM1, is proposed to bind to methylated DNA and to function in the AGO4 effector complex