RNA Predating the Development of DNA Still Carries out Complex Cellular Biochemistry
Offline Dangerous Bacterium Hosts Genetic Remnant of Life's Distant Past
ScienceDaily (Aug. 15, 2010) — Within a dangerous stomach bacterium, Yale University researchers have discovered an ancient but functioning genetic remnant from a time before DNA existed, they report in the August 13 issue of the journal Science.
To the surprise of researchers, this RNA complex seems to play a critical role in the ability of the organism to infect human cells, a job carried out almost exclusively by proteins produced from DNA's instruction manual.
"What these cells are doing is using ancient RNA technology to control modern gene expression," said Ron Breaker, the Henry Ford II Professor of Molecular, Cellular and Developmental Biology at Yale, investigator for the Howard Hughes Medical Institute and senior author of the study.
In old textbooks, RNA was viewed simply as the chemical intermediary between DNA's instruction manual and the creation of proteins. However, Breaker's lab has identified the existence and function of riboswitches, or RNA structures that have the ability to detect molecules and control gene expression -- an ability once believed to be possessed solely by proteins. Breaker and many other scientists now believe the first forms of life depended upon such RNA machines, which would have had to find ways to interact and carry out many of the functions proteins do today.
The new paper describes the complex interactions of two small RNA molecules and two larger RNA molecules that together influence the function of a self-splicing ribozyme, a structure many biologists had believed had no role other than to reproduce itself. The new study, however, suggests that in the pathogenic stomach bacterium Clostridium difficile, this RNA structure acts as a sort of sensor to help regulate the expression of genes, probably to help the bacterium manipulate human cells.
"They were though to be molecular parasites, but it is clear they are being harnessed by cells to do some good for the organism," Breaker said.
This is the sort of RNA structure that would have been needed for life exist before the evolution of double-stranded DNA, with its instruction book for proteins that carry out almost all of life's functions today. If proteins are necessary to carry out life's functions, scientists need to explain how life arise without DNA's recipe. The answer to the chicken or egg question is RNA machines such as the one identified in the new study, Breaker said.
"A lot of sophisticated RNA gadgetry has gone extinct but this study shows that RNA has more of the power needed to carry out complex biochemistry," Breaker said. "It makes the spontaneous emergence of life on earth much more palatable."
http://www.sciencedaily.com/releases/2010/08/100812151630.htm
"Experiments are the only means of knowledge at our disposal. The rest is poetry, imagination." Max Planck
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I read something a while ago that was pointing to RNA possibly having roles as information carrier and enzyme in early organisms, this article is pointing the same way.
Zen-atheist wielding Occam's katana.
Jesus said, "Suppose ye that I am come to give peace on earth? I tell you, Nay; but rather division." - Luke 12:51
Wait didnt RNA evolve into DNA ?
As Clostridium are almost exclusively obligate anaerobes, thus meaning that they are direct descendants of microbes living before the Oxygen Crisis, it isn't surprising that they have quite a few metabolic and evolutionary left overs of the oxygen-free primordial life-forms.
“A meritocratic society is one in which inequalities of wealth and social position solely reflect the unequal distribution of merit or skills amongst human beings, or are based upon factors beyond human control, for example luck or chance. Such a society is socially just because individuals are judged not by their gender, the colour of their skin or their religion, but according to their talents and willingness to work, or on what Martin Luther King called 'the content of their character'. By extension, social equality is unjust because it treats unequal individuals equally.” "Political Ideologies" by Andrew Heywood (2003)
How's it going? Hope all well.
I've been dodging this insane 104°F heat wave in addition to the 80%+ humidity all thanks to what meteorologists call the "North Atlantic Oscillation" (sauna-like conditions, basically)
I imagine it's fairly cold where you are, depending on how far south you live...
“A meritocratic society is one in which inequalities of wealth and social position solely reflect the unequal distribution of merit or skills amongst human beings, or are based upon factors beyond human control, for example luck or chance. Such a society is socially just because individuals are judged not by their gender, the colour of their skin or their religion, but according to their talents and willingness to work, or on what Martin Luther King called 'the content of their character'. By extension, social equality is unjust because it treats unequal individuals equally.” "Political Ideologies" by Andrew Heywood (2003)
Interesting article! I find the self-splicing ribozyme to be of note here. Should any replication errors turn up, they can be bad,neutral or exploitable. I think that we all know where that might go.
The only thing is that I don't fully follow where the RNA first world really makes all that much sense.
In the chemical stew that must have been present, it seems to me that polymers of all types must have formed randomly at first. A single amino acid could get associated weakly with three nucleotides for example. Then too, amino acids can polymerize and if they do so on the peptide bonds, that paves the way for more longer strings of RNA, which of course would catalyze ever more of the source polypeptides. Let a polypeptide form that can also catalyze the beginning of a lipid membrane and the whole thing is off to the races as it were.
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about 24C I would think - very warm for our late winter. If it was the weekend I'd go sailing. Instead here I am at work, procrastinating.
"Experiments are the only means of knowledge at our disposal. The rest is poetry, imagination." Max Planck