VIGILIN, A UBIQUITOUS PROTEIN WITH 14 K-HOMOLOGY DOMAINS, IS THE ESTROGEN-INDUCIBLE VITELLOGENIN MESSENGER-RNA 3'-UNTRANSLATED REGION-BINDING PROTEIN

RNA-binding proteins containing KH domains are widely distributed. One KH domain protein of unknown function, vigilin (also known as the hig h density lipoprotein-binding protein), contains 14 KH domains and is ubiquitous in vertebrate cells. We previously used RNA gel mobility sh ift assays to describe an estrogen-inducible protein which binds speci fically to a segment of the 3'-untranslated region (3'-UTR) of vitello genin mRNA, an area which has been implicated in the estrogen-mediated stabilization of vitellogenin mRNA, Here we show that the vitellogeni n mRNA-binding protein (VitRNABP) is vigilin. The VitRNABP was isolate d as a 150-155-kDa protein on a vitellogenin mRNA 3'-UTR affinity colu mn. Peptide microsequencing revealed that the purified protein was vig ilin, a conclusion confirmed in Western blot analysis with antibodies to vigilin. Direct confirmation that vigilin is the VitRNABP was obtai ned from RNA gel mobility shift assays which demonstrated that antibod ies to chicken vigilin supershifted the Xenopus VitRNABP band. Xenopus liver vigilin mRNA and the VitRNABP exhibited similar induction by es trogen, providing additional confirmation that vigilin is the estrogen -inducible protein which binds to the 3'-UTR of estrogen-stabilized vi tellogenin mRNA. These data support a role for vigilin in the hormonal control of mRNA metabolism.