# Structures of RNA Processing and Silencing Enzymes in Prokaryotes

> **NIH NIH R01** · FLORIDA STATE UNIVERSITY · 2020 · $353,838

## Abstract

Description: The recent discovery that bacteria and archaea employ an RNA-guided DNA cleavage
mechanism to defend themselves from invasive genetic elements offers an unprecedented opportunity
for understanding fundamental microbial biology and for developing biotechnology tools. Clustered,
regularly interspaced, short palindromic repeats (CRISPR) loci encode three types of mechanistically
different RNA-guided DNA cleavage enzymes that degrade invasive DNA while avoiding self-DNA.
Understanding the molecular mechanisms of how these distinct DNA cleavage enzymes control
their activities has important implications in basic enzymology, antibiotics resistance epidemics,
human microbiome research, and genome editing. The Li laboratory has identified and purified
representative members of two major types (Types II and III) of CRISPR-Cas DNA cleavage enzymes
and is poised to unveil novel molecular mechanisms as well as to develop useful tools. Though both
types are RNA-guided and invader-specific, these nucleases have drastically different in enzyme
composition and activation mechanisms. An integrated approach ranging from cell-based assays, to
structural biology and to fundamental enzymology will be employed to compare and contrast the mode
of DNA interference by these nucleases, leading to an understanding of how microbe impact human
health and biosphere and to an ultimate goal of developing CRISPR-based technology. The Li
laboratory has assembled a team of scientists with complementary expertise in microbiology, nucleic
acid biochemistry, mammalian cell biology, X-ray crystallography, and high-throughput cryogenic
electron microscopy, in order to maximize the impact while mitigating risks of the research.
Relevance: The CRISPR elements are found in more than 40% bacteria and are critical to
maintenance of the overall microbial environment. The frequent occurrence of CRISPR in medically
important bacteria that include but not limited to Yersinia pestis, Mycobacterium tuberculosis,
Haemophilus influenzae, Helicobacter pylori, Neisseria meningitides, Vibrio vulnificus, Staphylococcus
aureus, Salmonella Typhi, Clostridium tetani, and human microbiome relates CRISPR directly to human
health. A thorough understanding of the CRISPR immunity has important implications in eradicating
virulence and creating new antimicrobial strategies. While one of the CRISPR enzymes, namely Cas9,
has been repurposed to serve as a user-specified genome-editing tool with ever-increasing popularity,
we are yet to unleash the full potential of the CRISPR-derived tools in biomedical applications. The
proposed research is aimed at overcoming current limitations while expanding the capability.

## Key facts

- **NIH application ID:** 9881186
- **Project number:** 5R01GM099604-08
- **Recipient organization:** FLORIDA STATE UNIVERSITY
- **Principal Investigator:** Hong Li
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $353,838
- **Award type:** 5
- **Project period:** 2012-05-01 → 2021-12-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9881186

## Citation

> US National Institutes of Health, RePORTER application 9881186, Structures of RNA Processing and Silencing Enzymes in Prokaryotes (5R01GM099604-08). Retrieved via AI Analytics 2026-05-26 from https://api.ai-analytics.org/grant/nih/9881186. Licensed CC0.

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