Expression of recombinant human ceruloplasmin--an absolute requirement for splicing signals in the expression cassette.

We report the successful expression of recombinant human ceruloplasmin which was made possible by inclusion of splicing signals in the expression vector. Ceruloplasmin cDNA expressed from the vector pNUT in baby hamster kidney cells gave protein yields of 0.03 mg/l which increased to 15 mg/l with splicing signals present. The defect in expression from the intronless cDNA is due to complete retention of ceruloplasmin mRNA in cell nuclei. The block to cytoplasmic export is alleviated by splicing signals, allowing full expression of the mRNA.