Transcript Regulation of the Recoded Archaeal α-l-Fucosidase In Vivo

Abstract

Genetic decoding is flexible, due to programmed deviation of the ribosomes from standard translational rules, globally termed “recoding”. In Archaea, recoding has been unequivocally determined only for termination codon readthrough events that regulate the incorporation of the unusual amino acids selenocysteine and pyrrolysine, and for −1 programmed frameshifting that allow the expression of a fully functional α-l-fucosidase in the crenarchaeon Saccharolobus solfataricus, in which several functional interrupted genes have been identified. Increasing evidence suggests that the flexibility of the genetic code decoding could provide an evolutionary advantage in extreme conditions, therefore, the identification and study of interrupted genes in extremophilic Archaea could be important from an astrobiological point of view, providing new information on the origin and evolution of the genetic code and on the limits of life on Earth. In order to shed some light on the mechanism of programmed −1 frameshifting in Archaea, here we report, for the first time, on the analysis of the transcription of this recoded archaeal α-l-fucosidase and of its full-length mutant in different growth conditions in vivo. We found that only the wild type mRNA significantly increased in S. solfataricus after cold shock and in cells grown in minimal medium containing hydrolyzed xyloglucan as carbon source. Our results indicated that the increased level of fucA mRNA cannot be explained by transcript up-regulation alone. A different mechanism related to translation efficiency is discussed.

Programmed Deviations of Ribosomes From Standard Decoding in Archaea

“…However, since there are no α-L-fucosidase genes regulated by PRF in Bacteria and Eukarya, it has been suggested that this sophisticated mechanism of translational regulation preexisted in S. solfataricus and it was applied to the α-L-fucosidase gene for physiological reasons. Very recently, it has been found that fucA1 mRNA increases by 10 fold after S. solfataricus undergoes cold shock and in S. solfataricus cells grown in minimal medium containing the oligosaccharides of the hemicellulose xyloglucan (De Lise et al, 2021). Furthermore, this α-L-fucosidase has been shown to cooperate with other glycoside hydrolases from S. solfataricus for the hydrolysis of fucosylated xyloglucan oligosaccharides by removing the fucose moieties from this substrate with high efficiency in vitro (Curci et al, 2021).…”