| Abstract: | Polysomal RNA was extracted from human term placenta and total poly(A)-containing RNA purified by affinity chromatography on oligo(dT)-cellulose. Poly(A)-containing RNA constituted approximately 1.2% of the total polysomal RNA and 8% of this purified preparation was able to anneal with [3H]poly(U). When injected into Xenopus oocytes, this poly(A)-rich RNA directed the synthesis of a polypeptide which is immunoprecipitable with a specific antiserum to human placental lactogen. The identity of authentic human placental lactogen and the immunoreactive polypeptide synthesized in the oocytes is suggested by their identical behaviour in dodecylsulfate gel electrophoresis and by the formation of identical cyanogen bromide peptides. No precursor of human placental lactogen can be detected in the oocytes. The messenger RNA for human placental lactogen is very stable in oocytes; it is translated efficiently for a period of at least 7 days. |
