# Engineering of PPR base editors to repair pathogenic SNPs at the level of RNA

> **NIH NIH R15** · CALIFORNIA STATE UNIVERSITY LOS ANGELES · 2021 · $438,000

## Abstract

Abstract
Many pathogenic T-to-C SNPs have been identified in humans including several in the
mitochondrial genome linked to Leigh syndrome. The mitochondrial genome is especially
difficult to manipulate using existing gene editing technologies due to inefficient transfer of guide
RNAs through the mitochondrial membranes. The organelle genomes of most land plants
contain hundreds of ancient T-to-C mutations that are “repaired” by C-to-U RNA editing before
translation to produce functional proteins. The sufficient editing apparatus in plants has been
recently discovered to be comprised of a single protein with an RNA binding PPR tract domain
and a C-terminal catalytic domain called the DYW domain. The PPR domains follow a
combinatorial code where two polar amino acid positions strongly influence the ribobase
recognized. Changes in the polar amino acids have been correlated with predictable changes in
RNA substrate specificity making the PPR domains programable. This grant aims to reprogram
plant PPR editing factors to recognize human SNPs. In the first aim of the proposal, the editing
factor PPR65 will be manipulated through engineered amino acid changes in the PPR domains
to target mitochondrial pathogenic SNPs. In a second aim, local sequence requirements
imposed by the enzymatic domain will be investigated and DYW domain swapping experiments
should identify a catalytic domain with the least sequence bias. Catalytic sequence bias could
potentially limit application of repair of human SNPs and the diversity of targeted sequences in
higher plants suggest such bias is not universal. Both aims seek to apply the plant RNA editing
machinery to make specific base edits to improve human health. Advantages in using the plant
system include the prevention of permanent off-target effects through RNA recognition by the
PPR tract and a fully proteinaceous, compact structure that can theoretically be efficiently
delivered to mitochondria. This project will also provide research opportunities for six under-
represented minority students in biochemistry each semester. Primary research will foster
excitement for biochemistry and lead to a greater equity into the backgrounds of students
prepared for STEM careers.

## Key facts

- **NIH application ID:** 10359636
- **Project number:** 1R15GM144905-01
- **Recipient organization:** CALIFORNIA STATE UNIVERSITY LOS ANGELES
- **Principal Investigator:** Michael Lloyd Hayes
- **Activity code:** R15 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $438,000
- **Award type:** 1
- **Project period:** 2021-09-20 → 2025-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10359636

## Citation

> US National Institutes of Health, RePORTER application 10359636, Engineering of PPR base editors to repair pathogenic SNPs at the level of RNA (1R15GM144905-01). Retrieved via AI Analytics 2026-06-14 from https://api.ai-analytics.org/grant/nih/10359636. Licensed CC0.

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