Spaghetti-like proteins SAID1/2 become stiff to brake microRNA machinery

What is it about?

MicroRNAs (miRNAs) are a group of tiny but powerful molecules that guide their protein partners to the target messenger RNAs, resulting in target cleavage or failure in protein synthesis. Hundreds of miRNAs are present in plants to regulate plant growth, development, and responses to biotic and abiotic stresses. In plants, miRNAs are made from the primary substrates (pri-miRNAs) by the machinery composed of the RNase III enzyme DCL1, double-stranded RNA binding proteins HYL1, and the multifaced zinc finger protein SE. Here we have uncovered the spaghetti-like proteins SAID1/2 (SE-Associated Inhibitors with Dwarfism appearance in the mutants) as a brake for the machinery. SAID1/2 sequester pri-miRNAs and inhibit the operation of the microprocessor machinery. Of note, SAID1/2 themselves are less-structured, spaghetti-like proteins predicted by artificial intelligence. However, SAID1/2 can also condensate on SE and promote phosphorylation and degradation of SE, leading to the double inhibition of miRNA production.

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Photo by Önder Örtel on Unsplash

Photo by Önder Örtel on Unsplash

Why is it important?

MicroRNAs, the 21-24 nucleotides non-coding RNAs that control gene expression via cleavage or translational inhibition of target mRNAs. However, too much is as bad as too little, dysregulation of miRNA production often leads to multiple developmental defects and affects adaption/well-being of plants and human being. Whereas much have been known about the process of miRNA production, negative regulation that restrain miRNAs from over-production remains fully unclear. This study unexpectedly identified the less-structured proteins SAID1/2 act as such brake pad to block the miRNA production machinery to prevent miRNA over-production. The finding provides a new way to improve miRNA-regulated agronomic traits.

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