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Many eukaryotic cells contain large ribonucleoprotein particles in the cytoplasm known as vaults. The vault complex comprises the major vault protein , two minor vault proteins , and a variety of small untranslated RNA molecules known as vault RNAs only found in higher eukaryotes. These molecules are transcribed by RNA polymerase III.
Given the association with the nuclear membrane and the location within the cell, vaults are thought to play roles in intracellular and nucleocytoplasmic transport processes. A study, using cryo-electron microscopy, has determined that vtRNAs are found close to the end caps of vaults. This positioning of the RNA indicates that they could interact with both the interior and exterior of the vault particle. Overall, the current belief is that the vtRNAs do not have a structural role in the vault protein, but rather play some kind of functional role. However, while there has been an expanding body of research on vtRNA, there has yet to be a solid conclusion on the exact function.