# Engineering CRISPR-Cas proteins for conditional and robust interrogation of the genome

> **NIH NIH R01** · UNIVERSITY OF CALIFORNIA BERKELEY · 2022 · $304,046

## Abstract

Project Summary
Cas9 is an RNA-guided DNA-targeting endonuclease. Its programmability facilitates two extremely useful
functionalities that were previously difficult to engineer: the introduction of either a DNA double strand
break or recruitment, via fusion, of a protein effector to a desired location in the genome. As a
consequence, Cas9 has revolutionized both gene editing and functional interrogation of the genome.
Despite this potential, a number of issues constrain Cas9's utility. Its uncontrolled nature limits both on-
target endonuclease activity and the ability to promote the most desirable form of genome editing,
homologous recombination. Relatedly, Cas9's natural function as an endonuclease is not necessarily
congruent with that of a modular fusion protein scaffold and many effector fusions fail to elicit reliable
activity. The goal of our work is therefore to create the next-generation of CRISPR-Cas proteins that
enable finely-controlled genome editing activity and robust fusion protein activity. We have recently
developed a series of tools, fashioned around transposon-mediated recombination, that facilitate the
construction and isolation of highly engineered Cas9 fusion proteins. Using these tools, we have
engineered an allosterically regulated Cas9. Here, using this and optimized variants, we propose to
investigate how precise temporal control of Cas9 can improve the desired activities of on-target cutting
and homologous recombination. With regards to fusion protein construction, we have preliminary data
suggesting that the topology of Cas9 can be altered using circular permutation which, in principle,
provides a new class of protein scaffolds for effector recruitment. We propose to systematically map
Cas9's potential for circular permutation across its primary sequence and use these non-natural variants
to improve one class of highly useful Cas9-effectors, transcriptional activators. Finally, in the course of
our preliminary experiments, we have serendipitously discovered that circular permutation allows the
construction of gated Cas9 proteins that are activated upon specific proteolytic cleavage. We propose to
develop these molecules as a new class of genome editing tool and demonstrate their utility in a model
system of viral infection in planta. If successful, these experiments will address several of the major
challenges facing the genome editing community today: how to reduce off-target effects, increase
homologous recombination activity, and exploit the programmable nature of Cas9-fusion proteins to their
full extent.

## Key facts

- **NIH application ID:** 10333376
- **Project number:** 5R01GM127463-04
- **Recipient organization:** UNIVERSITY OF CALIFORNIA BERKELEY
- **Principal Investigator:** David Frank Savage
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $304,046
- **Award type:** 5
- **Project period:** 2019-04-05 → 2023-01-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10333376

## Citation

> US National Institutes of Health, RePORTER application 10333376, Engineering CRISPR-Cas proteins for conditional and robust interrogation of the genome (5R01GM127463-04). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10333376. Licensed CC0.

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