In vitro nuclear import

The nuclear pore serves as the gateway to the nucleus, allowing molecules to slip in and out. A technique devised by Larry Gerace (Scripps Research Institute in La Jolla, California) and colleagues helped researchers ferret out the biochemical details of nuclear import and export, identifying the driving force as the protein Ran. The same system helped scientists pinpoint the proteins that ferry cargo into the nucleus.

In the early 1990s, cell biologists knew that proteins need the right credentials to gain admission to the nucleus—a short string of amino acids called the nuclear localization sequence (NLS). But the mechanism that shuttled cargo through the pore remained mysterious. To study the question, Gerace and colleagues created a new system. The only available procedure, which used Xenopus egg extracts, yielded a nuclear envelope with functional...