Polyadenylylation and transcription following fertilization

Polyadenylylated RNA from sea urchin embryos concomitantly labeled with [(3)H]adenosine and [(14)C]uridine between fertilization and the four-cell stage was used to determine whether the RNA primers prerequisite to the massive polyadenylylation known to occur after fertilization are synthesized during oogenesis or subsequent to fertilization. Characterization of this RNA and unlabeled RNA via retention on nitrocellulose membranes and poly(U)-impregnated filters, molecular hybridization with [(3)H]poly(U), RNase resistance, oligo(dT)-cellulose chromatography, and size-distribution studies indicates that the poly(A) tracts synthesized after fertilization are predominantly appended to preexisting cytoplasmic primers of oogenic origin. Hence, if polyadenylylation is involved in the selective editing of presumptive genetic messages, this process is not confined to the nucleus unless a given codogenic transcript can undergo more than one cycle of adenylylation.