This bud's for you: mechanisms of cellular nucleocytoplasmic trafficking via nuclear envelope budding.

The nuclear envelope (NE) physically separates the cytoplasmic and nuclear compartments. While this barrier provides advantages, it also presents a challenge for the nuclear export of large ribonucleoprotein (RNP) complexes. Decades-old dogma holds that all such border-crossing is via the nuclear pore complex (NPC). However, the diameter of the NPC central channel limits the passage of large cargos. Here, we review evidence that such large RNPs employ an endogenous NE-budding pathway, previously thought to be exclusive to the nuclear egress of Herpes viruses. We discuss this and other models proposed, the likelihood that this pathway is conserved, and the consequences of disrupting NE-budding for synapse development, localized translation of synaptic mRNAs, and laminopathies inducing accelerated aging.