There are 64 genetic combinations (43), because there are four bases arranged in threes. Each of the three codons code for one amino acid, of which there are 20 commonly used in proteins. This difference of 64 versus 20 is called degeneracy, and it has always been a mystery. Some amino acids have a single codon, but others can be encoded with up to six codons. Is unemployment a “frozen danger,” as Francis Crick thought? Could there be functional reasons why a gene might specify one codon instead of another?
In the past, we have reviewed the growing evidence of the breakdown process. We learned that different codons work at different rates, providing a “speed limit” to how proteins are made. Casey Luskin has documented how different codons give the cell “translational pauses” that affect folding rates with phenotypic consequences. Last year, we saw that some codons have effects on circadian rhythms. Jonathan McLatchie spoke of further evidence of positive adjustment in sex. As Luskin said, “The theory of intelligent design predicts that living things will have a lot of information, and thus encourages us to look for new sources of important information that work in genes.”
We have another fulfillment of that prophecy. Research at MIT found “Newly discovered genes [that] controls bacterial survival during infection” (emphasis added.” This code-in-a-code uses redundant codons to signal bacteria to change their stress response strategy: “entering a sleep-like state that allows them to survive in hostile environments when deprived of oxygen or nutrients.” A team led by Peter Dedon, a professor of biological engineering at MIT, discovered this by working with Mycobacterium bovis.
Complementary RNAs
In fact, codons affect their corresponding RNA (tRNA) in different ways. Consider first how complex the RNA system is:
Once a tRNA molecule is made, it is converted and many different chemical reactions. These changes are believed to influence how tightly the tRNA anticodon binds to the mRNA codon on the ribosome.
In this study, Dedon and colleagues found that certain tRNA mutations increased significantly when the bacteria were deprived of oxygen and stopped growing.
While testing the bacteria’s response to anoxic conditions, the researchers wondered if other codons made a difference. They knew that “the amino acid threonine can be added by ACU, ACC, ACA, or ACG,” so they hunted to find possible links to the stress response.
One of these changes was found in the ACG threonine anticodon, so the researchers analyzed the entire genome. Mycobacterium bovis looking for genes with the highest percentage of that ACG codon compared to other threonine codons. They got that genes with high levels of ACG included a family known as DosR regulon, which contains 48 genes that are essential for cells [sic] stop growing and live in a dormant state.
When oxygen is lacking, these bacterial cells begin to release more proteins from the DosR regulon, while producing proteins from genes that have one of the other codons for threonine drops. DosR regulon proteins guide the cell into a dormancy-like state by shutting down the cell’s metabolism and stopping cell division.
Here, it is strong evidence of different effects when the same amino acid is replaced by another codon. The work of the Dedon group is published in Nature Communicationan accessible newspaper.
Values of Protein Products
Apparently, the ACG codon affects the “wobble” of the corresponding tRNA and how tightly the amino acid binds. This, in turn, affects the efficiency of translation on the ribosome, thus controlling the rate of protein production. They began to see the maddening process of destruction, which is highlighted in the phrase “integrated system”:
Codon re-engineering dosR exaggerates the hypoxia-induced changes in the translation of DosR at the codon, with mutants. dosR revealing feelings unintended consequences with bacterial survival during hypoxia. These results reveal a coordinated system of tRNA mutations and translation of codon-biased transcripts that enhance the expression of stress response proteins. by mycobacteria.
Finally, they elaborate on this interconnected system, stating that it represents another form of genetics:
There is an emerging hypothesis of the existence of ‘coding codons’. based on specific codon genes that can control translation. Among possible methods linking environmental changes with codon-oriented translation, recent studies have shown that many of the tRNA-modified ribonucleosides form a dynamic system that responds to cellular stress. We have shown that stress-specific mutations in tRNA wobble modified, viz can extend or reduce tRNA decoding ability, helping to identify underutilized or underutilized cognate codons in mRNAs, which it increases translation length and leads to selection and downregulation of codon-biased genes.
A report from MIT does not hesitate to call this a “newly discovered genetic code” or “another genetic code” with a functional meaning, namely “another aspect of controlcarried by RNA, which helps cells to divert resources quickly in an emergency.” One biochemist speaks of the significance of the discovery:
“The writers are there a remarkable example of new biology, emerging deep in the transfer of RNAswhich translates the genetic code in all living things to produce proteins,” says Paul Schimmel, a professor of cell and molecular biology at the Scripps Research Center, who was not involved in the research. viewed in a simple, straightforward manner for decades. They produce a strong, comprehensive analysis to show that there are skins and skins, deeper, in this work of translation.“
ID statement
That’s from a clever list of creative estimates. As strong as the evidence was in favor of tRNA-mediated gene translation, it was not strong enough. Scientists are now beginning to see “stages and groups, deeper” in its complexity. “It’s really just another type of geneticsin which any gene family required to change a cell’s phenotype is enhanced by specific codons,” Dedon says.” And he believes that this is not just an issue.
Interested in other papers with design implications? Check these out:
Boris Zinshteyn and Rachel Green, write Sciencethink “When Stop Makes Sense.” They investigate why, in contrast to the “standard” of genes, “codons” sometimes specify amino acids. “Answers to this problem may shed light on the termination of translation and gene regulation in all eukaryotes,” they say.
Sandra Wolin, who writes in the book Bulletin of the National Academy of Sciencesinvestigates RNA-editing enzymes that act as chaperones, helping tRNAs fold into the correct structure. “Because nucleotide changes can also stabilize RNA structure and influence folding pathways,” he says, “it will be exciting and challenging to tease out the relative contributions of each function and the ways in which these two components interact and reinforce each other.”
It was first published in 2016.
#Crazy #weak