YPEL4 (yippee-like 4) belongs to a family of five yippee-like proteins, all of which localize to the centrosome or mitotic spindle and are widely expressed in both adult and fetal tissue. This localization plus the fact that the family of human YPEL proteins share a high degree of sequence homology across species suggests that these proteins may have a conserved function involved in cell division. YPEL4 is ubiquitously expressed in adult tissues and has been shown to associate with the major vault protein (MVP). It has been suggested that MVP can inhibit YPEL4's ability to activate Elk-1 in the MAPK signaling pathway.