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December 8, 2014

Short DNA sequences enable bacterial enzyme to identify foreign DNA

Short DNA sequences known as "PAM" (for protospacer adjacent motif--shown in yellow) enable the bacterial enzyme Cas9 to identify and degrade foreign DNA during viral infections, as well as induce site-specific genetic changes in animal and plant cells. The presence of PAM is also required to activate the Cas9 enzyme. Cas9 plays an essential role in the bacterial immune system and is fast becoming a valuable tool for genetic engineering.

A team of researchers at Lawrence Berkeley National Lab used a combination of single-molecule imaging and bulk biochemical experiments to show how the RNA-guided Cas9 enzyme is able to locate specific 20-base-pair target sequences within genomes that are millions to billions of base pairs long.

This research was primarily supported by grants from the National Science Foundation and the National Institutes of Health.

To learn more about this research, see the Berkeley Lab news story Puzzling question in bacterial immune system answered. (Date of Image: 2012)

Credit: Illustration by KC Roeyer

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