Fig. 4. A long poly(A) tail is not sufficient to overcome BRE-mediated repression. Translation efficiency of chimeric osk-lacZ mRNAs bearing either no poly(A) tail or a tail of >200A in ovary extract. The transcripts used in these experiments bear the 5' region of osk mRNA up to the second AUG codon, and either the wild-type osk 3'UTR (WT) or an osk 3'UTR from which the BREs were deleted (ABC). The data shown are representative of three independent experiments. The values were normalized for those of a luciferase RNA co-translated as an internal control and the experimental error varies between 3% and 10%.