Recombinant polypeptides transplanted from pUMA vector-derived cRNAs are translocated through microsomal membranes and exported out of frog oocytes.

pSP64 derivatives were constructed to obtain cloning vectors suitable for in vitro transcription and subsequent in vitro synthesis of recombinant proteins equipped with N-terminal signal sequences. The amino acid sequence of the signal peptide was adapted and slightly modified from the one occurring in the neural cell adhesion molecule, NCAM. Its ability to direct recombinant proteins into secretory pathways was tested by in vitro translation in microsomal membrane-containing reticulocyte lysates and by injection of the pUMA-derived cRNAs into Xenopus laevis oocytes.