Pul, U, Wurm, R, Arslan, Z, Geissen, R, Hofmann, N and Wagner, R (2010) Identification and characterization of E. coli CRISPR-cas promoters and their silencing by H-NS. Mol. Microbiol. 75:1495-512
Inheritable bacterial defence systems against phage infection and foreign DNA, termed CRISPR (clustered regularly interspaced short palindromic repeats), consist of cas protein genes and repeat arrays interspaced with sequences originating from invaders. The Cas proteins together with processed small spacer-repeat transcripts (crRNAs) cause degradation of penetrated foreign DNA by unknown mechanisms. Here, we have characterized previously unidentified promoters of the Escherichia coli CRISPR arrays and cas protein genes. Transcription of precursor crRNA is directed by a promoter located within the CRISPR leader. A second promoter, directing cas gene transcription, is located upstream of the genes encoding proteins of the Cascade complex. Furthermore, we demonstrate that the DNA-binding protein H-NS is involved in silencing the CRISPR-cas promoters, resulting in cryptic Cas protein expression. Our results demonstrate an active involvement of H-NS in the induction of the CRISPR-cas system and suggest a potential link between two prokaryotic defence systems against foreign DNA.
Base Sequence; DNA/metabolism; Escherichia coli/genetics; Escherichia coli/physiology; Escherichia coli Proteins/biosynthesis; Escherichia coli Proteins/genetics; Escherichia coli Proteins/metabolism; Fimbriae Proteins/metabolism; Gene Expression Regulation, Bacterial; Gene Order; Gene Silencing; Inverted Repeat Sequences; Models, Biological; Molecular Sequence Data; Multigene Family; Promoter Regions, Genetic; RNA, Bacterial/biosynthesis; Transcription Initiation Site; Transcription, Genetic
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