miRNAs Get Flipped
On a couple other blogs, a study published in Science by Joan Steitz1 is being called “One of the biggest findings of the year,” and “If it turns out to be true, this finding just flipped the whole field on its head.” Bitesize Bio would be greatly remiss to not mention to so hot a story, joining in with The Daily Transcript and One Random Scientist.
The abstract, from Switching from Repression to Activation: MicroRNAs Can Up-Regulate Translation:
AU-rich elements (AREs) and microRNA target sites are conserved sequences in mRNA 3′-untranslated regions (3′UTRs) that post-transcriptionally control gene expression. Upon cell-cycle arrest, the ARE in tumor necrosis factor–{alpha} (TNF{alpha}) mRNA is transformed into a translation activation signal, recruiting microRNP-associated factors Argonaute (AGO) and fragile-X-mental-retardation –related protein 1 (FXR1). We show that human microRNA miR369-3 directs association of these proteins with the ARE to activate translation. Furthermore, we document that two well-studied microRNAs — Let-7 and the synthetic microRNA cxcr4 — likewise induce translation up-regulation of target mRNAs upon cell-cycle arrest; yet, they repress translation in proliferating cells. Thus, activation is a common function of microRNPs upon cell-cycle arrest. We propose that translation regulation by microRNPs oscillates between repression and activation during the cell cycle.
For further reading on why this is so contradictory to everything known about miRNAs, check out Timothy Nilsen’s2 review in TRENDS in Genetics. Then compare that with the reaction on One Random Scientist.
- Vasudevan S, Tong Y, Steitz JA. Switching from Repression to Activation: MicroRNAs Can Up-Regulate Translation. Science [accepted 2 Nov, 2007] DOI: 10.1126/science.1149460
- Nilsen TW. Mechanisms of microRNA-mediated Gene Regulation in Animal Cells. TRENDS in Genetics May 2007; 23(5):243-249. DOI: 10.1016/j.tig.2007.02.011
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Dan Rhoads
Dan is an American working in industry in a small Mediterranean country. He has a BSc in Molecular Biology and a PhD in Cancer Pharmacology and Biochemistry.
December 4th, 2007 at 2:40 pm
Not my field, but still very interesting.