Advancing genome editing through studying DNA repair mechanisms

Date:
February 9, 2022
Source:
CeMM Research Center for Molecular Medicine of the Austrian Academy
of Sciences
Summary:
Prime editing is an improved variant of the CRISPR/Cas system that
can introduce alterations in DNA with exquisite precision. But
the method is complex and inefficient. A research group has now
been able to show that the DNA mismatch repair process plays an
essential role in prime editing.



FULL STORY ========================================================================== Prime editing is an improved variant of the CRISPR/Cas system that can introduce alterations in DNA with exquisite precision. But the method
is complex and inefficient. The research group of Joanna Loizou, at the
Medical University of Vienna and the CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, has now been able to
show that the DNA mismatch repair process plays an essential role in
prime editing.


========================================================================== Since the discovery of CRISPR/Cas9, also known as molecular scissors, scientists around the world have been working to improve the revolutionary technique for altering DNA that earned Emmanuelle Charpentier and
Jennifer Doudna the Nobel Prize in 2020. The method enables deep
exploration of the human genome and shows enormous potential for curing
genetic diseases. While the precise alterations made by CRISPR/Cas9
were initially less predictable, scientists around the world are now
working on further developments that enable precise changes to be made
within DNA. A recent study by the group of Joanna Loizou, Group Leader
at the Center for Cancer Research at MedUni Vienna and CeMM Adjunct
Principal Investigator, was devoted to understanding how prime editing,
a technique that promises greater targeting accuracy and efficiency in introducing DNA changes, can be made more efficient and precise.

Prime editing is a powerful genome engineering tool that allows for replacement, insertions, and deletion of DNA into any given genomic locus.

However, to date, the efficiency of prime editing has been highly
variable and depends not only on the targeted genomic region but also
on the genetic background of the edited cell. Leading authors Joana
Ferreira da Silva, CeMM PhD student, and Gonc,alo Oliveira from the
Center for Cancer Research of the MedUni Vienna, devoted their study to
the question of which factors influence the success of prime editing,
taking a close look at DNA repair processes.

Since genome editing relies on the intrinsic DNA repair machinery within a cell, it is imperative to know which DNA repair pathways are engaged and
how this impacts the outcome of editing. Yet the underlying DNA repair machinery involved in prime editing is largely unknown. The study authors explain: "Depending on the type of DNA damage, a cell has different
cellular repair mechanisms. To find out which of these are active in prime editing, we performed a targeted genetic screening for DNA repair factors covering all known repair pathways." Study leader Joanna Loizou adds,
"Our results show that the DNA repair pathway, known as mismatch repair, influences prime editing outcomes. This is the pathway that deals with
base mismatches in the genome. Depending on the cell line, type, and site
of edit we want to make, we can increase the efficiency of prime editing
by 2 to 17-fold by eliminating mismatch repair." Specifically, the study
showed an accumulation of the proteins MLH1 and MSH2 -- proteins involved
in the DNA mismatch repair process and each responsible for recognition
and removal of the incorrect base -- at the site of genome editing.

The results show that the activity of the mismatch repair proteins
inhibits the efficiency of prime editing. "By removing the activity of the mismatch repair pathway from a cell, we show that the efficiency of prime editing can be increased, and its accuracy improved," Loizou said. This fundamental understanding will ultimately bring this technology closer
to the clinic.

========================================================================== Story Source: Materials provided by CeMM_Research_Center_for_Molecular_Medicine_of_the Austrian_Academy_of_Sciences. Note: Content may be edited for style
and length.


========================================================================== Journal Reference:
1. J. Ferreira da Silva, G. P. Oliveira, E. A. Arasa-Verge,
C. Kagiou, A.

Moretton, G. Timelthaler, J. Jiricny, J. I. Loizou. Prime editing
efficiency and fidelity are enhanced in the absence of mismatch
repair.

Nature Communications, 2022; 13 (1) DOI: 10.1038/s41467-022-28442-1 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/02/220209093357.htm

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