So based off of conversations in James Tour at McGovern Medical School in Houston, I’d like to start a new discussion on the current state of Origins of Life research and specifically the role of RNA.
James Tour has suggested a moratorium on OoL research as, in his view, it hasn’t gotten anywhere in the last 50 years.
Most people outside of biology, including myself, only get a very limited picture of OoL research. Basically a paragraph or two on the Miller-Urey experiment and very speculative “this is how it might have been” statements.
So, I’m looking for:
an brief overview of the state of the field
some sort of estimate as to “progress” as that is a critique
This may be too brief, but a concise summation of the state of the field (that being RNA and the origins of life) is that the ability of RNA to serve as both information and catalyst strongly supports the hypothesis that places RNA at the beginnings of life. In particular, the fact that the core of the ribosome, the peptidyl transferase active site, is RNA and not protein places an RNA at the very heart of life. The peptidyl transferase itself roots the tree (or bush) of life, and it is hard to describe an OOL scenario that does not flow through this ribozyme.
Of course, questions remain. The article posted by @Rumraket does a nice job of describing some of the open issues regarding the origins of the first RNA (an issue that is yet to be resolved), and I won’t copy and paste them at the moment. @Paul_Nelson gave us a link (below) to a talk by Loren Williams (who can be tracked down on Pubmed or Google) whose work is getting at the cooperation between RNA and amino acids/peptides/polypeptides, which seems to me to be the logical step in the progression from RNA to RNA/protein to life as we know it. I guess what I find interesting in Williams’ work is the possibility that the “naked RNA world”, in which RNA and only RNA was catalyst, may have been fleeting, and perhaps non-existent. This area is still developing, but I believe is going to progress remarkably over the next few years. Of course, there is much, much more research, and many more people who I should mention but cannot (owing to the vastness of the subject, and the scope of the post). Others should add to this, if for no other reason than to provide balance to my own personal preferences in this area.
As far as progress, it is not surprising that things go in fits and starts, and that the underworld of day-to-day research proceeds slowly at times. However, the RNA world hypothesis has given us one of the crucial (perhaps THE crucial) pieces of the OOL puzzle - namely that the peptidyl transferase is a ribozyme, and that this ribozyme is poised at the crucial point in the OOL. Other hypotheses, models, and mechanisms must pass through (in a manner of speaking) this enzyme; it must sit at the end of mechanisms that describe the origins of RNA, and it must be at the beginning of processes by which life as we know it evolved. For the OOL field, I think this discovery is more important that Miller-Urey.
This really helps put things in context better for me, thanks.
This may be a very dumb question, but I’ll throw it out there anyway. If RNA serves a both information and catalyst, why is DNA needed? If I remember right DNA is more stable than RNA (single stranded, extra hydroxyl group in the nucleotides) but is that it?
I agree completely. Whether you accept the hypothesis or not, this is the strongest piece of evidence that RNA preceded the current DNA/RNA/protein “design.”
It’s such strong evidence that despite the presence of an entire chapter on the RNA World, a reader depending on Meyer’s Signature in the Cell for evidence will never learn that peptidyl transferase is a ribozyme.
I would love to see anyone’s explanation of this as an intelligent design choice.