Initiation of Translation in halophilic Archaea.

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Translation is a very important step in the expression of genetic information. Four mechanisms for translation initiation are known, i.e. the Shine-Dalgarno motif-based mechanism used by bacteria and archaea, the scanning mechanism and the IRES-depending mechanism of eukaryotes, and initiation at leaderless transcripts. We dis-covered that the majority of haloarchaeal transcripts are leaderless and that only very few leadered transcripts contain a SD sequence. Initation on SD-less leadered transcript is distinct from all previously known path-ways, therefore a novel mechanism exists at least in haloarchaea. Molecular characterization of translation initiation in haloarchaea is a major focus of the proposed research, including mutagenesis of initiation elements, characterization of differential usage of the three initiation mechanisms, and conditional depletion of initiation factors. Regulation of translation typically occurs during initiation, which is rate-limiting. Translational regulation in haloarchaea requires both 5’- and 3’-UTRs. The mechanism of translational regulation in haloarchaea will be analyzed, including global analysis of regulation, characterization of RNA elements, and identification of regulatory factors.