To produce mature ribosomal RNAs (rRNAs), the catalysts that control protein synthesis in all cells, the body first needs perfectly formed intermediate or pre rRNAs, which can be further processed into fully functioning ones. The intermediate form is produced as an RNA transcript that is cleaved or cut in multiple steps to produce mature rRNA.
"While we believe that this switch is essential for ribosome assembly, it seems unlikely that this is the only event that regulates cleavage," Karbstein said. "However, tight regulation of ribosome synthesis is essential to ensure the structural integrity of mature ribosomes."
Cutting Extra Material
The ribosomal RNA that is transcribed has extra material in it, Karbstein said, so it is necessary to cut it down that's why these cuts or cleavages are so essential to the process of producing the final rRNA product.
The study also suggests RNA itself exploits its own natural ability to form these stable structural switches to order and regulate various RNA-dependent biological processes.
"What is interesting," Karbstein said, "is that as the organism becomes more complex, the number of cleavages needed increases. This may make the process more accurate and that may be an evolutionary advantage, but even in bacteria this cutting is not done in a simple way. We still don't know exactly why that is."
Perhaps these strictly ordered cleavage steps are introduced to produce singularly perfect intermediates, she added. This is important because cleavage is an irreversible energy-releasing process with the potential to shift the landscape of assembly towards the final product. As a result, cleavage steps should be carefully controlled and should only occur if the assembly intermediate is correct.
"Ribosomes make mistakes rarely, on the order of one in 10,000 amino acid changes," Karbstein said. "A lot of this accuracy depends on conversati
|Contact: Mika Ono|
Scripps Research Institute