Scientists discover protist with non-canonical genetic code
Updated
Updated · ScienceDaily · May 7
Scientists discover protist with non-canonical genetic code
4 articles · Updated · ScienceDaily · May 7
The pond organism, found in Oxford University Parks, uses TAA for lysine and TAG for glutamic acid, leaving TGA as its only stop codon, the team reported in PLOS Genetics.
Researchers made the accidental finding while testing a single-cell DNA sequencing pipeline, and identified suppressor tRNA genes supporting the codon reassignments in the previously unknown ciliate species Oligohymenophorea sp. PL0344.
The discovery challenges assumptions that TAA and TAG change together and adds to evidence that ciliates are hotspots for genetic code evolution, suggesting microbial eukaryotes may be more genetically flexible than thought.
Nature has been hacking the genetic code for eons. Are scientists just catching up to what microbes already perfected?
The 'universal' genetic code has exceptions. How many of life's other fundamental rules are waiting to be broken?
AI is learning from biological data we are about to lose. Are we building our future on a crumbling foundation?
Unprecedented Stop Codon Reassignment in Protists Reveals Dynamic Genetic Code Plasticity and Viral Defense Mechanisms
Overview
Recent discoveries in protists reveal radical changes to the genetic code, challenging its long-held universality. The parasitic protist Blastocrithidia nonstop reassigns all three standard stop codons to amino acids, using UAA uniquely as the sole stop signal, while its mitochondria maintain the standard code by blocking suppressor tRNAs. Meanwhile, Oligohymenophorea sp. PL0344 decouples UAA and UAG stop codons, assigning them to lysine and glutamic acid, respectively, and relies on tandem UGA codons for termination. These genetic rewiring events likely evolved through neutral processes and proteomic constraints, providing advantages like viral defense and translational optimization. Inspired by these natural genetic firewalls, synthetic biology is advancing virus-resistant cells and novel protein engineering, while astrobiology adapts to the possibility of diverse genetic codes beyond Earth.