The 5′ untranslated region of fruA mRNA is required for translational enhancement of FruA synthesis during Myxococcus xanthus development
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The fruA gene encodes a DNA-binding response regulator protein essential for the development of Myxococcus xanthus. This gene is transcribed with an unusually long (235 nucleotides) 5′ untranslated region (UTR) that has been shown to be absolutely necessary for the induction of FruA synthesis during development. With lacZ as a reporter, it was found in this report that each regional deletion mutation within 5′ UTR caused a decrease in β-galactosidase production. Base substitution mutations that were designed to alter local stem-loop structures also decreased fruA-lacZ expression, however their compensatory mutations could not rescue fruA-lacZ expression at all. A moderate decrease in β-galactosidase activity was observed from the fruA-lacZ transcriptional fusion lacking fruA 5′ UTR; in contrast, expression of the fruA-lacZ translational fusion lacking the 5′ UTR was severely impaired. In addition, both the amount and stability of fruA-lacZ mRNA were just moderately reduced in the absence of this 5′ UTR. These results suggest that the function of the 5′ UTR of fruA mRNA requires integrity of almost the entire region and may depend on the primary sequence. More importantly, fruA 5′ UTR modulates the expression of its own gene mainly by enhancing translation efficiency of the transcript.
KeywordsMyxococcus xanthus fruA gene Untranslated region Translational control
Open reading frame
We thank one of the manuscript reviewer for pointing out that the result of Δ56–109 suggests translation of the uORF may not be required for translation of fruA.
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