The origin of life, how does RNA link proteins?

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13.8 billion years ago, the universe exploded. This is the beginning of all historical dates, where the story of creation begins. 4.6 billion years ago, the earth was born. 600 million years later, in the early ocean, the earliest life appeared, and organisms began a complex and long evolution from prokaryotes to eukaryotes. However, the origin of life has long been a mystery.

So far, people probably only know that DNA is the substrate of biology, because DNA carries various genetic information for building and operating organisms, while RNA acts as a messenger molecule, copying genetic instructions from DNA molecules, and then passing them to ribosomes. The molecular factory of cells, when the factory reads RNA genetic information, it starts to synthesize specific proteins.

That is, all organisms use the same genetic molecules—DNA and RNA—to store information. RNA has long been hypothesized to act as a precursor to DNA—if these simple molecules were present in the "primordial soup" of early Earth, they might have begun to replicate and diversify into a range of forms. As the molecules became more complex, RNA may eventually have given rise to the cells with DNA molecules that gave birth to all the life forms we see today .

Theories supporting this hypothesis include: RNA can self-replicate to meet the requirements of genetic material to transmit genetic information; RNA can not only serve as an important part of the ribosome structure, but also serve as the information between DNA and protein during the expression of genetic information ties; after scientists discovered ribozymes in protozoa Tetrahymena and other organisms, they have successively found that ribozymes are involved in the process of protein synthesis and mRNA processing.

As ingenious as this explanation is, it remains unknown whether RNA molecules can actually undergo this evolution . In fact, this hypothesis is not without problems. For example, RNA is a very fragile molecule, especially when it gets long. Furthermore, it is unclear how the connection between RNA molecules and the protein world arises, for which genetic material, as it is known, provides the blueprint.

Now, in a new paper published in the journal Nature, Carell's team has discovered a way in which this connection might occur.

First, RNA itself is a complex macromolecule. In addition to the four canonical bases A, C, G and U, which encode genetic information, it also contains non-canonical bases, some of which have very different structures. These non-information-encoding nucleotides are important for the functioning of RNA molecules.

At present, researchers have mastered more than 120 such modified RNA nucleosides. Carell's group believes that these non-canonical nucleosides are the key ingredients that connect the RNA world to the protein world.

Some of these molecular fossils, when located in RNA, can "decorate" themselves with single amino acids or even small chains of amino acids (peptides), the researchers say. This results in small chimeric RNA-peptide structures when an amino acid or peptide happens to be present in a solution at the same time as the RNA.

In such structures, the amino acids and peptides attached to the RNA then even react with each other, forming larger and more complex peptides. "In this way, we created RNA-peptide particles in the lab that could encode genetic information, and even longer peptides," Carell said.

Thus, ancient fossil nucleosides are somewhat similar to the nucleus in RNA, forming a core upon which long peptide chains can grow. On some strands of RNA, the peptide even grew at several points . According to the new theory, a decisive factor at the outset was the presence of RNA molecules, which could "decorate" themselves with amino acids and peptides, linking them into larger peptide structures.

That said, it's at least possible that RNA has undergone evolution and led to complex life, although that doesn't necessarily confirm that's how it happened in the real world. As our research on life sciences goes deeper and deeper, new research and new discoveries may, to a large extent, continue to rewrite our understanding of the existing knowledge system.