Frog oocyte nuclei are huge: 100,000 somatic nuclei could fit inside them. With size comes the threat of rupture. Markus Bohnsack, Dirk Görlich, and colleagues (Universität Heidelberg, Germany) find that these nuclei are protected from breakage by a network of intranuclear actin filaments.
The German team had previously defined exportin 6 (Exp6) as a nuclear export protein with only one known cargo: β-actin. “I asked my post-doc to do the most boring experiment—to test if exportin also exported α-actin and γ-actin,” says Görlich. “The experiment was not just boring but very frustrating—he couldn't see any export of any substrate.”
Export failed because Bohnsack was using frog oocytes, and this cell type turns off Exp6 production. Adding back Exp6 restored actin export but made the nuclei so fragile that they could rarely be isolated intact. “It was this series of frustrations that got us into something...
