Staying limber is crucial not just for yoga enthusiasts, but for cells installing nuclear pores, as Scarcelli et al. report on page 799. They identify a protein that helps the passageways assemble by boosting the flexibility of the nuclear membrane.

Every molecule that enters or exits the nucleus passes through a nuclear pore complex. How cells build these channels remains murky, however. Scarcelli et al. chanced on a key contributor because of their interest in how cells export RNA from the nucleus. That process goes awry in yeast missing the protein Apq12.

Cooling Apq12-lacking cells inhibited their growth, the researchers found, in part because mutant cells can't assemble nuclear pores. Instead, many of their pore proteins, particularly those from the filaments, clustered in the cytoplasm. Warming the cells allowed them to fashion complexes again and sent the mislocalized proteins back to become part of new pores.

One way that cells cope with lower temperatures is to alter the composition of the nuclear membrane to maintain its flexibility. Scarcelli et al. hypothesized that Apq12-deficient yeast can't make that adjustment. To test the idea, the researchers exposed the cells to benzyl alcohol, which slips into the membrane and loosens it up. The alcohol spurred the out-of-place pore proteins to return to their normal locations. The work indicates that Apq12's job is to maintain membrane flexibility. The researchers now want to determine how the protein performs that task.