Octopuses have surprised scientists once again with a biological feature not identified in any other animal studied so far. Researchers have discovered that ribosomes – the microscopic cellular factories that translate genetic instructions into proteins – have an unusual structural break in certain octopus species. Instead of remaining continuous as it does in almost all other animals, the core 28S ribosomal RNA is split into two pieces that continue functioning together. Even more remarkable is the effect of this modification: octopus ribosomes read genetic instructions more accurately and make fewer mistakes when selecting the amino acids used to construct proteins. Laboratory experiments showed that octopus ribosomes interacted with nearly correct but incorrect transfer-RNA molecules about four times less strongly than squid ribosomes. When researchers engineered a comparable break into E. coli bacterial ribosomes, the accuracy of protein synthesis roughly doubled without slowing protein production. The experiments also revealed reduced accumulation of incorrectly folded proteins, an especially important advantage in nervous tissue, where protein aggregates can gradually damage cells.
The discovery may be connected to another extraordinary characteristic of cephalopods – their extensive ability to edit RNA after genetic information has been copied from DNA. Octopuses and squid are known to modify tens of thousands of sites within protein-coding RNA, allowing different versions of proteins to be produced from the same underlying genes. Such flexibility could be particularly important for their sophisticated nervous systems, but extensive RNA editing also creates additional opportunities for errors when genetic instructions are translated. Researchers suggest that the unusually accurate octopus ribosome may therefore act as a protective system, allowing extensive RNA editing without overwhelming cells with faulty proteins. Intriguingly, this mechanism appears to have emerged in the evolutionary lineage of more recently derived octopuses with expanded nervous systems roughly 100 million years ago, while the same structural break was absent from the deep-sea octopus relatives examined. Scientists still do not know precisely how cells create the split, and they caution that many of the functional experiments were performed outside a living animal. Nevertheless, the discovery could ultimately have significance far beyond octopus biology. Understanding how cells improve the accuracy of protein production and prevent misfolded proteins from accumulating could eventually provide new clues for research into diseases involving harmful protein aggregates, including neurodegenerative disorders.
