Abstract
Synthesis and assembly of ribosomal components are fundamental cellular processes and generally well-conserved within the main groups of organisms. Yet, provocative variations to the general schemes exist. We have discovered an unusual processing pathway of pre-rRNA in extreme thermophilic archaea exemplified by Pyrococcus furiosus. The large subunit (LSU) rRNA is produced as a circularly permuted form through circularization followed by excision of Helix 98. As a consequence, the terminal domain VII that comprise the binding site for the signal recognition particle is appended to the 5´ end of the LSU rRNA that instead terminates in Domain VI carrying the Sarcin-Ricin Loop, the primary interaction site with the translational GTPases. To our knowledge, this is the first example of a true post-transcriptional circular permutation of a main functional molecule and the first example of rRNA fragmentation in archaea.
Highlights
Synthesis and processing of rRNA is fundamental to all living organisms
We conclude from RiboMeth-seq analysis that the predominant form of large subunit (LSU) rRNA in P. furiosus is circularly permuted
We have shown by high-throughput sequencing as well as by northern blotting and primer extension that the main form of LSU rRNA in P. furiosus is circularly permuted
Summary
Synthesis and processing of rRNA is fundamental to all living organisms. A highly conserved feature at the transcriptional level is that the two main species, SSU and LSU rRNAs, are co-transcribed with the consequence that they are expressed directly into 1:1 stoichiometry. 5S rRNA on the other hand can be part of the same transcriptional unit or transcribed elsewhere in the genome. 5S rRNA on the other hand can be part of the same transcriptional unit or transcribed elsewhere in the genome. Another common principle applies to early pre-rRNA processing, namely that the 5 ́ and 3 ́ ends of each of SSU and LSU rRNA comes together as a prerequisite for their release from the ribosomal precursor. Bulge-Helix-Bulge (BHB) motifs are formed, cleaved by tRNA splicing endonuclease, and ligated by tRNA ligase to form circular intermediates. This is followed by further endonucleolytic cleavages and exonucleolytic trimming to form the mature rRNA ends. The details of pre-rRNA processing and variations on the general schemes have been the subject
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