The effect of capping and polyadenylation on the stability, movement and translation of synthetic messenger RNAs in Xenopus oocytes.

Synthetic RNAs coding for chicken lysozyme, calf preprochymosin and Xenopus globin were transcribed in vitro using Sp6 RNA polymerase. The effects of capping and adding a poly(A) tail on the stability, movement and translation of these RNAs in Xenopus oocytes was examined. Capping and polyadenylation increased stability of the transcripts, with at least 40% remaining intact 48 h after injection into oocytes. Capped poly(A)- transcripts moved more rapidly in oocytes than either capped poly(A)+ transcripts or naturally occurring mRNAs. The translational efficiency of most of the synthetic RNAs in oocytes increased with both capping and polyadenylation. The exception was one Xenopus globin transcript which had an unusual 3' end of 20As and 30Cs, where further polyadenylation decreased translational efficiency. Polyadenylation was essential for detectable expression of the synthetic RNAs in cultured cells, but decreased translation of the synthetic RNAs in vitro.