Everyone appreciates a little extra support now and then, and a new study shows that miRNAs, or more specifically their seed regions, do too. The report in NAR uncovered that micro-ribonucleoprotein complexes (miRNPs) get miRNAs ready to take care of their mRNA targeting business by shoring up the structure of miRNA seed regions, which is way less shady than the court-ordered or creepy sugar-daddy kinds of support that we normally hear about.
Scientists from UC Santa Cruz, spearheaded by Nicole Lambert, learned about how miRNPs (made up of argonaute proteins) get miRNAs ready for action with Selective 2’-Hydroxyl acylation Analyzed by Primer Extension (SHAPE) assays that test nucleotide reactions to the chemical NMIA in order to track RNA backbone flexibility and base-pairing abilities of the bound miRNAs. What they saw was that miRNPs create a support structure to keep seed regions rigid and able to pair up with their target mRNA, while leaving the 3’ end in a flexible state. Here’s some other things they discovered:
- Argonaute proteins only shield bases 1-7 from NMIA, keeping only that region in a rigid conformation.
- miRNA bases outside of the seed region have higher reactivity with NMIA, and therefore more flexibility, than even unbound miRNA, meaning miRNPs not only lock down the seed region, but they loosen up everything else.
- The miRNP complex structure keeps miRNAs from unintended interactions with themselves or other molecules.
- Correct miRNP organization of the seed region structure makes miRNAs able to sequence specifically target mRNAs.
Showing the crucial structural support that miRNP complexes arrange and organize in order for miRNA seed regions to do their job brings us one step closer to unraveling the miRNA mechanism once and for all.
Show your miRNA support by checking out the full article at Nucleic Acids Research, February 2011.