RNA’s spatial structure allows it to replicate efficiently without enzymes, a feature that may explain why RNA, not DNA, was the first self-replicating molecule on Earth, according to Polish researchers from the Faculty of Chemistry at Wrocław University of Science and Technology.
“RNA’s ability to self-replicate in the absence of enzymes is another strong argument that RNA is more likely to have originated life than DNA,” said Rafał Szabla, PhD, who led the study.
The question of which molecules came first—DNA, RNA, or proteins—remains a central problem in understanding the origin of life. In modern cells, DNA stores genetic information, RNA transcribes and transports it, and proteins act as structural components and enzymes.
“My team and I are investigating the synthesis pathways of RNA and DNA monomers in prebiotic conditions. We are looking for answers to the question of how the first function of an information polymer could have arisen without the involvement of enzymes. In today's biochemistry, this process is tightly controlled by protein machinery. We want to determine whether, before the first enzymes appeared, information polymers were capable of self-replication,” Szabla said.
New findings show that the secondary structure of RNA makes it particularly suited for enzyme-free replication. Barbara Lech, PhD candidate and co-author, explained:
“We have two main types of helices: the A-type RNA helices, and the B-type DNA helices. The A-type helix is more compressed and condensed. The B-type helix is more extended and looks ‘more elegant’—that is what we associate with images depicting the genetic code in pop culture,” she said.
Computer simulations indicate that RNA’s compact A-type helices allow monomers to fit more tightly into template cavities, enabling efficient replication. DNA, with its more spacious B-type helices, allows monomers to wobble, making self-replication without enzymes inefficient.
Experiments inspired by Australian research confirm this effect. When DNA monomers are placed on an RNA template, replication occurs efficiently because RNA imposes its tight A-type helicity on the structure, promoting the copying process.
Szabla added: “Other forms of nucleic acids considered in synthetic biology cannot perform the same function as RNA. Without its presence, they cannot self-replicate effectively. This is another strong argument for the so-called RNA world hypothesis—the theory that this macromolecule played a key role in the emergence of complex biochemistry and, subsequently, life on Earth.”
Although the research focuses on basic science, it could influence technology. Understanding RNA replication without enzymes may simplify DNA synthesis in the lab. Current methods, such as polymerase chain reaction (PCR), require expensive enzymes. Enzyme-free replication methods could reduce costs and streamline laboratory procedures.
PAP - Science in Poland, Ludwika Tomala
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