The tumor suppressor protein PTEN dephosphorylates both proteins and phosphoinositide lipids and regulates many cellular processes including growth, motility, and apoptosis. Although a few PTEN-interacting proteins have been identified, its many putative regulatory domains suggest additional interactions that may affect PTEN function. Yu et al. have determined that PTEN interacts the vault complex, the largest known ribonucleoprotein particle described to date. Specifically, the C2 domain of PTEN interacts with two EF hands of the major vault protein (MVP), one of the three constituent proteins of the vault complex. Endogenous PTEN colocalized with vault complex particles when cell lysates were fractionated and both proteins immunoprecipitated when overexpressed in cultured cells. PTEN also associated with MVP in a calcium-dependent manner in vitro. The structure of the vault complex shows a hollow interior that is thought to facilitate transport and sequestration, or both, of proteins. The authors speculate that PTEN could get into the nucleus through its association with the vault complex.