At PhysOrg a new article review puts the kabash on the RNA-world hypothesis.
“I’m convinced that the RNA world (hypothesis) is not correct,” Caetano-Anollés said. “That world of nucleic acids could not have existed if not tethered to proteins.”
Also
“This is a very engaging and provocative article by one of the most innovative and productive researchers in the field of protein evolution,” said University of California at San Diego research professor Russell Doolittle, who was not involved in the study. Doolittle remains puzzled, however, by “the notion that some early proteins were made before the evolution of the ribosome as a protein-manufacturing system.” He wondered how – if proteins were more ancient than the ribosomal machinery that today produces most of them –”the amino acid sequences of those early proteins were ‘remembered’ and incorporated into the new system.”
We, too, remain “puzzled” as to how all of this came about via undirected processes.
Here’s the paper.
Another day; another bad day for Darwinism. (So much to explain, and so little to explain it with!!)
Here’s the corrected URL for the paper.
Sorry — not sure how that previous URL got butchered.
Maybe the second time’s a charm. Try here.
Sure wish WordPress had a previewer…
Basically, this study argues that RNA metabolism, especially that involving primordial tRNAs and the parts of the SSU that work with tRNAs, pre-dates the peptidyl transferase (that is the core of the LSU). I don’t see how this is a problem for the RNA World.
Arthur: Look at Caetano’s quote above. He’s the preeminent researcher here, and he sees the RNAworld hypothesis as wrong.
Isn’t that a problem?
PaV, excuse me but in the Physorg article he appears to be saying that the RNA world required proteins, making it a “ribonucleoprotein world” and that this RNP world protein synthesis was accomplished via something that predated the ribosome and the PTC.
To quote directly from the abstract of Caetanos paper:
“Here we infer evolution of the structural components of the ribosome. Phylogenetic methods widely used in morphometrics are applied directly to RNA structures of thousands of molecules and to a census of protein structures in hundreds of genomes. We find that components of the small subunit involved in ribosomal processivity evolved earlier than the catalytic peptidyl transferase center responsible for protein synthesis. Remarkably, subunit RNA and proteins coevolved, starting with interactions between the oldest proteins (S12 and S17) and the oldest substructure (the ribosomal ratchet) in the small subunit and ending with the rise of a modern multi-subunit ribosome. Ancestral ribonucleoprotein components show similarities to in vitro evolved RNA replicase ribozymes and protein structures in extant replication machinery. Our study therefore provides important clues about the chicken-or-egg dilemma associated with the central dogma of molecular biology by showing that ribosomal history is driven by the gradual structural accretion of protein and RNA structures. Most importantly, results suggest that functionally important and conserved regions of the ribosome were recruited and could be relics of an ancient ribonucleoprotein world.”
I would think he tries to extend the RNA-world hypothesis to include a role for early peptides. About these peptides he suggests for instance the following things in the paper:
“Random polypeptides of the size of small proteins can fold into 3D conformations in the absence of selection [42]. Early peptides were therefore structured and likely rearranged and helped stabilize RNA, enabling rRNA structural conformations otherwise impossible by simple RNA-RNA interactions [43]. These changes induced small improvements in translation speed and accuracy …”
So instead of RNA he suggest RNA + random peptides. similar extensions of the RNa-world hypothesis have been put forth by other people earlier, see e. g. Cochrane and Strobel, RNA 2008, page 998, for RNA + coenzymes …
rna: “So instead of RNA he suggest RNA + random peptides….”
Yes. So now, not only do abiogenesis theorists need to explain how RNA came into existence, they also need to explain how peptides came into existence. Double the fun.
And then they need to show how they came to interact with each. Triple the fun.
Hi Bilbo,
Random peptides are no problem:
http://aghunt.wordpress.com/20.....rna-world/
Moreover, RNA-peptide interactions are also not that “improbable”. It’s pretty easy to find protein-binding RNA aptamers in rather modest collections of RNAs of random sequence.
I agree with rna’s comment, and would add (again): one idea proposed by Caetano-Annoles, that the SSU predates the LSU, is pretty interesting. Moreover, the suggestion that the origination and subsequent coevolution of the SSU-LSU RNA-RNA interface drove the larger evolution of the ribosome is also pretty interesting. After all, the origin of life is, at the end of the day, the origin of the ribosome. It’s exciting to think that this study may be shedding new insight into the most important single aspect of the history of life on earth.
It should be interesting to see how well these propositions stand up to further experimental evaluation.
Bilbo I
The point here is that the Caetano paper discussed here is not at all the blow against the rna-world hypothesis PAV suggests it to be.
The point here is that the Caetano paper discussed here is not at all the blow against the rna-world hypothesis PAV suggests it to be.
The only way PaV has been suggesting it’s a problem is by way of quote. To wit:
Apparently, your argument is with Caetano-Anolles.
OK so now it is known that there are two required macro-molecules- two very different types of macros.
And not any two will do. Even if you do get the two correct types, not just any two of those will do. Oh, and out of all the locations on Earth, these two have to be mingling.
No problemo… 😛