The 3′-untranslated region of human interleukin-8 mRNA suppresses IL-8 gene expression

摘要

Although adenosine/uridine (AU)-rich sequences in the 3′-untranslated region (UTR) of the interleukin-8 (IL-8) gene have been suggested to contribute to its post-transcriptional regulation, the molecular basis whereby this occurs still needs to be understood. To investigate the role of the 3′-UTR on human IL-8 gene regulation, chimeric reporter genes were generated by adding full length or differentially deleted 3′-UTR of the IL-8 gene to chloramphenicol acetyltransferase (CAT). Addition of the entire IL-8 3′-UTR markedly reduced CAT mRNA and protein expression in COS 7 cells. In a reporter gene study, IL-8 3′-UTR destabilized CAT mRNA, which was dependent on active transcription in COS 7 cells. A 357-base sequence (nucleotides (nt) 2387–2743 of genomic DNA) within 3′-UTR, designated >e, suppressed CAT gene expression by accelerating CAT mRNA turnover. A 26-base AU-rich sequence (nt 2552–2577) within >e, containing four AUUUA pentamers that form two UAUUUAUU and one UUAUUUAU octamers, did not suppress CAT gene expression. However, deletion of the AU-rich sequences attenuated the inhibitory effect of >e on CAT gene expression. Elimination of the first 100 bases (nt 2386–2486) attenuated the potency of fragment >e, but much weaker than elimination of the first 146 bases (nt 2387–2533). This study gives new insights in unravelling the molecular mechanisms involved in the post-transcriptional regulation of the IL-8 gene.