Doudna is a leading authority on RNA molecular structures who holds joint appointments with Berkeley Lab's Physical Biosciences Division and UC Berkeley's Department of Molecular and Cell Biology and Department of Chemistry. She is also an investigator with the Howard Hughes Medical Institute (HHMI). The results of this latest research on CRISPR are reported in the journal Science in a paper titled "Sequence- and structure-specific RNA processing by a CRISPR endonuclease." Co-authoring the paper with Doudna were Rachel Haurwitz, Martin Jinek, Blake Wiedenheft and Kaihong Zhou.
CRISPR is a unit of DNA, usually on a microbe's chromosome, made up of "repeat" elements, base-pair sequences ranging from 30 to 60 nucleotides in length, separated by "spacer" elements, variable sequences that are also from 30 to 60 nucleotides in length. CRISPR units are found in about 40-percent of all bacteria whose genomes have been sequenced, and about 90-percent of archaea. A microbe might have several CRISPR loci within its genome and each locus might contain between four and 100 CRISPR repeat-spacer units. Doudna and her colleagues studied CRISPR in Pseudomonas aeruginosa, a common bacterium that is ubiquitous in the environment.
Rachel Haurwitz, a graduate student in Doudna's research group and the first author on the Science paper, explains how the CRISPR/Cas immunity system works.
"When a bacterium recognizes that it has been invaded by a virus or a plasmid, it incorporates a small piece of the foreign DNA into one of its CRISPR units as a new spacer sequence. The CRISPR unit is then transcribed as a long RNA segment called the pre-crRNA. The Csy4 enzyme cleaves this pre-crRNA within each repeat element to create crRNAs about 60 nucleotides long that will contain sequences which match portions of the foreign DN
|Contact: Lynn Yarris|
DOE/Lawrence Berkeley National Laboratory