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Identification and characterization of E. coli CRISPR‐ cas promoters and their silencing by H‐NS
Author(s) -
Pul Ümit,
Wurm Reinhild,
Arslan Zihni,
Geißen René,
Hofmann Nina,
Wagner Rolf
Publication year - 2010
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2010.07073.x
Subject(s) - crispr , trans activating crrna , biology , promoter , crispr interference , gene , genetics , transcription (linguistics) , dna , gene silencing , microbiology and biotechnology , cas9 , gene expression , linguistics , philosophy
Summary Inheritable bacterial defence systems against phage infection and foreign DNA, termed CRISPR ( c lustered r egularly i nterspaced s hort p alindromic r epeats ), 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.