Cis-acting signals controlling translational initiation in the thermophilic archaeon Sulfolobus solfataricus

In this work, we have studied the in vitro translational features of a bici stronic mRNA of the extremely thermophilic Archaeon Sulfolobus solfataricus , with the aim of deter mining the nature of the cis-acting signals control ling the recognition of the translation initiation sites in the Archaea. We found that the most important feature for efficient initiation was the pre sence of a Shine-Dalgarno (SD)-like ribosome-binding motif, whose disruptio n entirely abolished the translation of the corresponding cistron. The infl uence of other features, such as the type of initiation codon, was variable and depended upon the gene and its position in the mRNA. However, the tran slational block caused by the disruption of the SD sequences could be remov ed by deleting the 5' untranslated region altogether, thereby creating a 'l eaderless' mRNA. This suggests that 'leaderless' initiation operates by a d efault mechanism that does not require a specific mRNA-rRNA interaction and may be common to all three primary domains of life.