Synthesis of organic building blocks in lab provide support for “RNA world”

 

At some point in the origin of life, an organic polymer must have self assembled according to basic principles of chemistry. The molecule that served as the precursor to complex life needed a particular skill set- it had to store information about itself and catalyze reactions to produce more such molecules. DNA is life’s primary information storage molecule, while a diverse assembly of proteins catalyze biological reactions. It turns out that RNA is the only existing molecule whose capabilities fit the profile. RNA is the the “functional” version of DNA, whose primary job in cells is to faithfully replicate DNA code and provide this code to specialized ribosomes that will translate it into proteins. Thus RNA is that is capable of not only storing coded information, but catalyzing its own replication much as an enzyme would catalyze a reaction.

Over the past several decades, scientists interested in life’s early origins have attempted to experimentally demonstrate the “RNA world hypothesis”.  The reconstruction of RNA components in early-Earth chemical conditions is a daunting task-  we can only speculate as to what those conditions were, and it seems likely that the conditions that allowed RNA to self assemble were quite specific. Recently, however, John Sutherland and colleagues seem to have made a breakthrough.  They were able to successfully synthesize active pyrimidine ribonucleotides- two of the four fundamental “letters” of genetic code- out of simple inorganic compounds. The conditions in which Sutherland’s lab produced ribonucleotides were consistent with “potential” early Earth geochemical models- not necessarily the chemical conditions that existed 4 billion years ago, but our best guess to date. This breakthrough lends the first real experimental support to the notion that long ago,  a prebiotic soup of RNA may have spontaneously assembled out of non-living molecules.

An artist's rendition of the RNA world theory. Shown here is a tRNA- a specialized RNA molecule that collects amino acids for protein assembly.

 

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