TRANSIENT POLYADENYLATION OF A MATERNAL MESSENGER-RNA FOLLOWING FERTILIZATION OF MOUSE EGGS

The molecular basis for the recruitment of maternal mRNAs after fertil ization is poorly understood since there is little information availab le regarding the identity of such mRNAs. An assay based on reverse tra nscriptase and PCR was used to identify a maternal mRNA that undergoes a transient polyadenylation after fertilization; the length of the po ly(A) tail increases from 40-80 adenosine (A) residues in the unfertil ized egg to approximately 250 3 h after insemination and then decrease s to about 180 around the time of pronucleus formation, that is 7 h af ter insemination. The DNA sequence of this cDNA, which encodes the pol yadenylation signal AAUAA, contains a uridine-rich sequence that may s erve as the cytoplasmic polyadenylation element observed in other mate rnal mRNAs that are recruited after fertilization.