Posted on 08/12/2010 4:22:51 PM PDT by decimon
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 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."
Primary ping.
yeah, sure they have. and if they look real hard, they'll find the Easter Bunny in there, too.
Looks like the “RNA world” hypothesis of abiogenesis just got another supporting data point.
Fray ping.
Your bailiwick, no?
I don't think so. They have only found another mechanism by which complex chemical reactions can be controlled. They only say that RNA is less complex because they do not understand how it works. And it only "appears" to be less complex than DNA.
The same kind of people say the appendix does not currently serve a purpose. I used to remember in high school they said that the appendix was "vestigial".
That is a strawman. RNA is more complex than DNA because it can perform enzymatic reactions. Although you are correct that less is understood about how it all works, because we are just now discovering miRNA’s, and the role they play in post transcriptional regulation of genes.
The fact that this RNA mechanism can act as a transcription factor IS a supporting data point for the “RNA world” hypothesis, because something like this would need to exist in order for there to be any sort of a complex ‘all RNA’ replicator.
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Thanks decimon!an ancient but functioning genetic remnant from a time before DNA existedTo all -- please ping me to other topics which are appropriate for the GGG list. |
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Yes, the appendix is a safe have for good bugs:
“Diseases causing severe diarrhea are endemic in countries without modern health and sanitation practices, which often results in the entire contents of the bowels, including the biofilms, being flushed from the body,” Parker said. He added that the appendix's location and position is such that it is expected to be relatively difficult for anything to enter it as the contents of the bowels are emptied.
“Once the bowel contents have left the body, the good bacteria hidden away in the appendix can emerge and repopulate the lining of the intestine before more harmful bacteria can take up residence,” Parker continued. “In industrialized societies with modern medical care and sanitation practices, the maintenance of a reserve of beneficial bacteria may not be necessary. This is consistent with the observation that removing the appendix in modern societies has no discernable negative effects.”
http://www.sciencedaily.com/releases/2007/10/071008102334.htm
Probably something that has a name with a “some”-suffix.
"Vestigial" does not necessarily mean having no function. An organ or feature can retain a purpose and still be sensibly called "vestigial" if that function is significantly reduced wrt ancestral and/or related organisms. This is certainly true of the human appendix. It is smaller and more degenerate wrt to related forms, and it's remaining functions are far less significant, and less essential, than providing for the full digestion of large quantities of raw vegetable matter.
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