Effect of short 5 ' UTRs on protein synthesis in two biological kingdoms

Efficient ribosomal protein synthesis is dependent on cis-acting elements i n the 5' untranslated region (UTR) of mRNAs. Between prokaryotes and eukary otes, the sequence and location of these elements differ to the extent of n ot being functionally interchangeable. We explored the possibility of const ructing bifunctional UTRs that could direct translation in both prokaryotes and eukaryotes. A variant of a UTR from ner of phage Mu (nei-ACC) enhanced protein synthesis in a rabbit reticulocyte lysate, and it was compared to a lacZ-CTA, containing the lambda cro RBS and the Escherichia coli lacZ spa cer. Several mutants in the -3 to -1 regions of both lacZ-CTA and ner-ACC w ere tested in rabbit reticulocyte lysate and E. coli to select UTRs that we re optimized simultaneously for both biological kingdoms. The lacZ-ATC prov ed 217-fold more effective than nei-ACC in this cross-species ability to en hance translation. The lacZ-ACC and ner-ATC were 83- and 78-fold, respectiv ely, better than nei-ACC. We conclude that short UTRs (12-15 nt in length) can be fine-tuned in the -9 to -1 regions to enhance protein synthesis conc urrently in prokaryotes and eukaryotes. In related studies, we show that nt at the -3 to -1 region of mRNAs exert an enormous impact on synthesis of p roteins in E. coli. (C) 1998 Elsevier Science B.V. All rights reserved.