Cell 134, 668–678 (2008) 10.1016/j.cell.2008.07.039

Editing a molecular tag called polyubiquitin sends two key immune-response proteins into the cellular garbage-disposal system.

There are two main ways of attaching one ubiquitin to another within polyubiquitin, and the one chosen often determines whether the target protein is activated or degraded. Vishva Dixit at Genentech in South San Francisco, California, and his team have made antibodies that can discriminate between the two.

Using these antibodies, they discovered that RIP1 and IRAK1 — proteins involved in a cell's response to immune-system signals — start out with the activating type of attachment, and that this is later 'edited' into the degrading one. This editing could be a way of dampening down other cell-signalling pathways.