South Korean researchers identify key mechanism for gene expression control via microRNA

A team of South Korean researchers has elucidated the intricate process by which microRNA (miRNA) activates the Argonaute protein, a crucial step in regulating gene expression. This breakthrough, led by Kim Bit-na-ri of the Institute for Basic Science (IBS) RNA Research Center and Noh Sung-hoon of Seoul National University's College of Life Sciences, marks the first time the specific activation mechanism has been identified globally.

miRNAs are small RNA molecules that play a vital role in controlling gene expression. They function by binding to messenger RNA (mRNA), thereby preventing specific proteins from being produced. However, this suppression can only occur when the miRNA combines with the Argonaute protein to form a 'protein-RNA complex,' known as RISC. While the binding of miRNA to Argonaute was known, the precise process of Argonaute activation remained unclear until now.

The research team discovered that a protein called 'chaperone' assists Argonaute in achieving its correct three-dimensional structure. Unexpectedly, they found that a complex formed by Argonaute and chaperones already exists within cells. By isolating and purifying this 'Argonaute maturation complex' (AMC), they observed that the chaperone holds Argonaute in an 'open' state, creating space for the miRNA to bind. Once the miRNA is bound, the chaperone detaches, completing the formation of Argonaute into its 'closed' state, ready to regulate genes.

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In reality, the box can only be folded once the item is used as a framework.

This finding challenges the previous assumption that the 'box' (Argonaute) could be pre-folded without the 'contents' (miRNA). The study reveals that the miRNA is not merely a binding partner but a key factor that enables Argonaute to achieve its functional structure. "In reality, the box can only be folded once the item is used as a framework," the researchers explained, highlighting that protein maturation is intrinsically linked to RNA binding.

The implications of this research are significant for the development of RNA therapeutics. Specifically, it is expected to enhance the design of small interfering RNA (siRNA) therapies, which work by selectively blocking the activity of specific genes to prevent the production of disease-causing proteins. Current siRNA therapy design relies on extensive trial-and-error synthesis and validation of thousands of combinations to improve stability in the body. By understanding the Argonaute binding process at a molecular level, researchers can now pursue more precise and potentially safer therapeutic designs. "This provides a molecular and theoretical basis for RNA therapy design, which has relied on trial and error," said Kim Bit-na-ri, anticipating the development of more efficient and secure siRNA treatments.

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This provides a molecular and theoretical basis for RNA therapy design, which has relied on trial and error.