cDNA cloning and disruption of the major vault protein alpha gene (mvpA) in Dictyostelium discoideum.

Vaults are large cytoplasmic ribonucleoprotein particles found in nearly all eukaryotic cells. Dictyostelium vaults contain two major proteins, MVP alpha (94.2 kDa) and MVP beta (approximately 92 kDa). Using an anti-rat vault antibody, we screened a Dictyostelium cDNA expression library and isolated a 2.8-kilobase pair clone that contained a single full-length reading frame. The identity of the clone was established by the presence of a predicted 20-amino acid sequence identical to that found in a peptide sequenced from purified MVP alpha. We have disrupted the single copy gene using homologous recombination and have demonstrated a loss of MVP alpha. Although the cells still produce MVP beta, they do not contain characteristic vault particles, suggesting that MVP alpha is required for normal vault structure. These cells should be a valuable tool for elucidating the function of vaults.