Rabbit a-globin messenger RNA translation by the mouse ovum

Fertilized mouse ova were injected with messenger RNA for rabbit globin. The ova were labelled with [H]leucine and the synthesized rabbit a-globin measured by immunoprecipitation. Injection of rabbit globin mRNA from 4-0 to 15-8pg/ovum resulted in the synthesis of ~1200 dpm/ovum of a-globin during an 18 h incubation. A concentration of mRNA that was translated below the maximum level of globin synthesis was used to determine translation efficiency. The efficiency of translation was 14-1 molecules of a-globin synthesized/cell/h for each molecule of a-globin mRNA injected. The radioactivity in a-globin was 1 % of the total incorporation in acid-precipitable material. Total incorporation of control and injected ova was not significantly different. This study shows that the fertilized mouse ovum can translate an injected foreign message with essentially the same efficiency as that reported for the Xenopus oocyte but substantially lower than the reticulocyte and that the translational capacity of the mouse fertilized ovum for injected mRNA is limited with little if any spare translational ability.