Shortening of the poly(A) tail at the 3'-end of mRNA requires its translation.

We report here that when alpha- or beta-globin mRNAs were hybridized with their alpha- or beta-complementary DNAs, respectively, and then translated in rabbit reticulocyte lysates, globin synthesis as well as shortening of the poly(A) tail were much less than that observed with nonhybridized mRNA. Furthermore, when the hybrid (alpha-globin mRNA/alpha-cDNA) was translated in the presence of nonhybrid (alpha-globin mRNA), the estimated average shortening of the poly(A) tails of the hybrid and the nonhybrid were 8% and 40%, respectively. Similar results were obtained when a hybridized beta-globin mRNA with beta-cDNA was incubated in the same translation mixture with beta-globin mRNA. No globin synthesis occurred in the mixtures containing the cDNA-mRNA hybrids only. In the mixtures containing both the hybrid and the nonhybridized mRNAs, globin was synthesized at a rate similar to that observed in a translation reaction mixture alone, that is, in the absence of any hybrid.