RNA chaperone activity of translation initiation factor IF1

Translation initiation factor IFI is an indispensable protein for translation in prokaryotes. No clear function has been assigned to this factor so far. In this study we demonstrate an RNA chaperone activity of this protein both in vivo and in vitro. The chaperone assays are based on in vivo or in vitro splicing of the group I intron in the thymidylate synthase gene (td) from phage T4 and an in vitro RNA annealing assay. IFI wild-type and mutant variants with single amino acid substitutions have been analyzed for RNA chaperone activity. Some of the IFI mutant variants are more active as RNA chaperones than the wild-type. Furthermore, both wild-type IFI and mutant variants bind with high affinity to RNA in a band-shift assay. It is suggested that the RNA chaperone activity of IFI contributes to RNA rearrangements during the early phase of translation initiation. (c) 2006 Elsevier Masson SAS. All rights reserved.