DNA's less famous brother

DNA has inspired many, many studies. But there is another nucleic acid that is often overlooked: RNA.

Scientists have long tried to find ways to target RNA in living cells, and now researchers at University of California, San Diego School of Medicine have found a way to do just that. By applying the popular DNA-editing technique CRISPR-Cas9 to RNA, they were able to track the movement of RNA inside a cell.


CRISPR-Cas9 is a bacteria that is also a naturally occurring defense mechanism that fends off other invading bacteria. Scientists use it to edit genes in mammalian systems.

This is achieved by having a "guide" RNA direct the Cas9 enzyme to the desired spot in the genome, where it cuts the DNA. This renders the gene inert, or allows researchers to replace the section adjacent to the cut with a corrected version of the gene.

Before, CRISPR-Cas9 was only used for DNA manipulation. In a study published March 17, 2016 in Cell, Senior author Gene Yeo, PhD, and colleagues have applied the technique to target RNA in live cells by altering features of the system. They designed a short nucleic acid called the PAMmer that helps direct Cas9 to an RNA molecule.

Yeo's team targeted specific RNA and watched as Cas9 fused with a fluorescent protein and revealed the movement of RNA into stress granules (a cluster of proteins and RNA that forms when the cell is under stress).

Notably, stress granules are linked to neurodegenerative disorders, such as ALS. This system allowed the team to track RNA over time without the need for artificial tags that interfere with normal cellular processes.

"Our current work focuses on tracking the movement of RNA inside the cell, but future developments could enable researchers to measure other RNA features or advance therapeutic approaches to correct disease-causing RNA behaviors." said Yeo.

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