[Endogenous synthesis of short-lived messenger-RNA-species in oocytes ofDysdercus intermedius Dist. after termination...

Non-ribosomal RNA is synthesized in oocytes of the telotrophicmeroistic ovary ofDysdercus intermedius Dist. during late oogenesis, 4-14 h before they become mature eggs. RNA is labelled "in vivo" by radioactive RNA precursors from a nucleotide pool which is established in the ooplasm prior to chorion-formation.RNA synthesized by late oocytes is characterized by a high turnover rate and appears first as a high molecular weight precursor which is converted during a few hours to smaller non-ribosomal RNA species of 30-5 S. In newly-laid eggs RNA molecules synthesized by the oocyte are no longer present. Their degradation products can be found within the nucleotide fraction. Thus, in contrast to RNA synthesized by trophocytes and stored in eggs in a stable form, endogeneously-formed RNA is not conserved for use in embryogenesis.Endogeneous RNA of oocytes is found to have a high content of poly(A)-segments. Fifty-seven percent of these are hybridizable with poly(U) immobilised on glassfiber filters. A few hours before the maturation of eggs, shortlived RNA synthesized by the oocyte is found in association with polysomes. By incubation of such polysomes in an "in vitro" protein-synthesizing system, polypeptides are formed which show a characteristic banding pattern after separation on SDS-polyacrylamide gels. The apparent molecular weights for the 4 main proteins are 65.000, 48.000, 44.000, and 40.000. There is no evidence for identity of any one of these proteins with a chorion protein.Some of the heterogeneous population of RNA molecules synthesized by late oocytes are characterized by a short lifetime, a relatively high content of poly(A) and the ability to activate protein synthesis "in vivo" or "in vitro", thus suggesting a function like that of mRNA.