MBG Journal Club: Presenter, Will Simmons

April 23, 2021 @ 3:00 pm – 4:00 pm

2020 / 2021 MBG Journal Club:


(Two Papers)

A programmable dual-RNA-guided DNA endonuclease in adaptive bacterial immunity  &

Multiplex genome engineering using CRISPR/Cas systems


Presentation by Will Simmons (Seydoux Lab)



Paper 1:


CRISPR/Cas systems provide bacteria and archaea with adaptive immunity against viruses and plasmids by using crRNAs to guide the silencing of invading nucleic acids. We show here that in a subset of these systems, the mature crRNA base-paired to trans-activating tracrRNA forms a two-RNA structure that directs the CRISPR-associated protein Cas9 to introduce double-stranded (ds) breaks in target DNA. At sites complementary to the crRNA-guide sequence, the Cas9 HNH nuclease domain cleaves the complementary strand while the Cas9 RuvC-like domain cleaves the non-complementary strand. The dual-tracrRNA:crRNA, when engineered as a single RNA chimera, also directs sequence-specific Cas9 dsDNA cleavage. Our study reveals a family of endonucleases that use dual-RNAs for site-specific DNA cleavage and highlights the potential to exploit the system for RNA-programmable genome editing.



Jinek, M., Chylinski, K., Fonfara, I., Hauer, M., Doudna, J.A., and Charpentier, E. (2012). A programmable dual-RNA-guided DNA endonuclease in adaptive bacterial immunity. Science 337, 816–821.

Link:   https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6286148/


Paper 2:


Functional elucidation of causal genetic variants and elements requires precise genome editing technologies. The type II prokaryotic CRISPR (clustered regularly interspaced short palindromic repeats)/Cas adaptive immune system has been shown to facilitate RNA-guided site-specific DNA cleavage. We engineered two different type II CRISPR/Cas systems and demonstrate that Cas9 nucleases can be directed by short RNAs to induce precise cleavage at endogenous genomic loci in human and mouse cells. Cas9 can also be converted into a nicking enzyme to facilitate homology-directed repair with minimal mutagenic activity. Lastly, multiple guide sequences can be encoded into a single CRISPR array to enable simultaneous editing of several sites within the mammalian genome, demonstrating easy programmability and wide applicability of the RNA-guided nuclease technology.


Cong, L., Ran, F.A., Cox, D., Lin, S., Barretto, R., Habib, N., Hsu, P.D., Wu, X., Jiang, W., Marraffini, L.A., et al. (2013). Multiplex genome engineering using CRISPR/Cas systems. Science 339, 819–823.

Link:  https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3795411/



Date/Time:  Friday, April 23, 2021, 3:00 PM


Journal Club Zoom link:


Meeting ID:  998 0819 2675  /  Passcode:  702009