期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 108, 期 50, 页码 20136-20141出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1113519108
关键词
defense mechanism; phage-host interactions; positive selection
资金
- Israel Science Foundation [611/10]
- Binational Science Foundation [2009218]
- German-Israel Foundation [2061/2009]
- Marie Curie International Reintegration Grants [PIRG-GA-2009-256340, GA-2010-266717]
Prokaryotic DNA arrays arranged as clustered regularly interspaced short palindromic repeats (CRISPR), along with their associated proteins, provide prokaryotes with adaptive immunity by RNA-mediated targeting of alien DNA or RNA matching the sequences between the repeats. Here, we present a thorough screening system for the identification of bacterial proteins participating in immunity conferred by the Escherichia coli CRISPR system. We describe the identification of one such protein, high-temperature protein G (HtpG), a homolog of the eukaryotic chaperone heat-shock protein 90. We demonstrate that in the absence of htpG, the E. coli CRISPR system loses its suicidal activity against. prophage and its ability to provide immunity from lysogenization. Transcomplementation of htpG restores CRISPR activity. We further show that inactivity of the CRISPR system attributable to htpG deficiency can be suppressed by expression of Cas3, a protein that is essential for its activity. Accordingly, we also find that the steady-state level of overexpressed Cas3 is significantly enhanced following HtpG expression. We conclude that HtpG is a newly identified positive modulator of the CRISPR system that is essential for maintaining functional levels of Cas3.
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