Analysis of the 5 ' and 3 ' UTRs in the post-transcriptional regulation ofthe interleukin-5 gene

Post-transcriptional regulation is emerging as an important control point i n cytokine gene expression. However, the role that it plays in IL-5 gene ex pression is unclear with some conflicting reports. Here we investigate the importance of posttranscriptional regulation and the role of the 5' and 3' untranslated regions (UTRs) in mIL-5 gene expression. To do this, IL-5 expr ession from a panel of cDNA constructs was compared. We found it essential to remove the 5' synthetic oligonucleotide tails, introduced during the clo ning of the mIL-5 cDNA, when studying IL-5 expression. The presence of thes e oligo(G) tails acted as potent inhibitors of translation of both SV40 and SP6 transcripts. Furthermore, the length of the tails was found to be crit ical to the translational efficiency. Taking this into account, we found no evidence to suggest that IL-5 is regulated at the level of mRNA stability or translation efficiency by either the 5' or 3'UTR. These results suggest that post-transcriptional control is not a major factor regulating IL-5 exp ression. (C) 1999 Elsevier Science B.V. All rights reserved.