The 3′-untranslated region of the human estrogen receptor α gene mediates rapid messenger ribonucleic acid turnover

Human estrogen receptor-alpha messenger RNA (hER alpha mRNA) has a relatively short half-life, which was determined to be approximately 5 h in MCF-7 cell line after actinomycin D treatment. The 3'-untranslated region (3'UTR) of hER alpha mRNA was previously shown to completely down-regulate chloramphenicol acetyltransferase activity when present at the 3'-end of chloramphenicol acetyltransferase transcripts, suggesting a destabilizing function of the hER alpha 3'UTR sequence. Chimeric genes composed of a serum-inducible Fos promoter, GH-coding sequences, and different segments of the hER alpha complementary DNA 3'UTR sequence were used to confirm this hypothesis and to localize the RNA region responsible for the destabilizing effect. The presence of the complete hER alpha 3'UTR reduced the half-life of the reporter mRNA from more than 24 to 3 h. When the hERa! 3'UTR was subdivided into four fragments (UTR1-4), one fragment, UTR2, retained the most ability to down-regulate the reporter mRNA (t(1/2) = 4 h). A stretch of four AUUUA motifs within UTR2 was shown not to mediate mRNA destabilization. In contrast, further subdivision of the UTRP into three parts (UTR2a-c) resulted in the loss of the destabilizing activity. Finally, recombination of two UTR2 subfragments (UTR2a and -b) partially restored this function, indicating a cooperative role among the three UTR2a-c subfragments in the process that leads to destabilization of the hER alpha transcript.