title: High-temperature protein G is essential for activity of the Escherichia coli clustered regularly interspaced short palindromic repeats (CRISPR)/Cas system.
abstract: 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 λ 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.
authors: Department of Clinical Microbiology and Immunology, Sackler School of Medicine,  Tel Aviv University, Tel Aviv 69978,  Israel.
authors: Ido
authors: I
authors: Yosef
authors: Moran G
authors: MG
authors: Goren
authors: Ruth
authors: R
authors: Kiro
authors: Rotem
authors: R
authors: Edgar
authors: Udi
authors: U
authors: Qimron
mesh_terms: D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism / Q000821:virology; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial / Q000235:genetics; D005820:Genetic Testing; D018841:HSP90 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006358:Hot Temperature; D055029:Inverted Repeat Sequences / Q000235:genetics*; D009154:Mutation / Q000235:genetics; D010957:Plasmids / Q000235:genetics; D039002:Prophages / Q000378:metabolism; D015203:Reproducibility of Results
chemical_list: D029968:Escherichia coli Proteins; D018841:HSP90 Heat-Shock Proteins; C489352:HtpG protein, E coli