A type III-Dv CRISPR-Cas system is controlled by the transcription factor RpaB and interacts with the DEAD-box RNA helicase CrhR
Raphael Bilger,
Angela Migur,
Alexander Wulf,
Claudia Steglich,
Henning Urlaub,
Wolfgang R. Hess
Affiliations
Raphael Bilger
Faculty of Biology, Genetics and Experimental Bioinformatics, University of Freiburg, Schänzlestrasse 1, 79104 Freiburg, Germany
Angela Migur
Faculty of Biology, Genetics and Experimental Bioinformatics, University of Freiburg, Schänzlestrasse 1, 79104 Freiburg, Germany
Alexander Wulf
Bioanalytics Research Group, Department of Clinical Chemistry, University Medical Centre, 37075 Göttingen, Germany; Bioanalytical Mass Spectrometry Group, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany
Claudia Steglich
Faculty of Biology, Genetics and Experimental Bioinformatics, University of Freiburg, Schänzlestrasse 1, 79104 Freiburg, Germany
Henning Urlaub
Bioanalytics Research Group, Department of Clinical Chemistry, University Medical Centre, 37075 Göttingen, Germany; Bioanalytical Mass Spectrometry Group, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany
Wolfgang R. Hess
Faculty of Biology, Genetics and Experimental Bioinformatics, University of Freiburg, Schänzlestrasse 1, 79104 Freiburg, Germany; Corresponding author
Summary: How CRISPR-Cas systems defend bacteria and archaea against invading genetic elements is well understood, but less is known about their regulation. In the cyanobacterium Synechocystis sp. PCC 6803, the expression of one of the three different CRISPR-Cas systems responds to changes in environmental conditions. The cas operon promoter of this system is controlled by the light- and redox-responsive transcription factor RpaB binding to an HLR1 motif, resulting in transcriptional activation at low light intensities. However, the strong promoter that drives transcription of the cognate repeat-spacer array is not controlled by RpaB. Instead, the leader transcript is bound by the redox-sensitive RNA helicase CrhR. Crosslinking coupled with mass spectrometry analysis and site-directed mutagenesis revealed six residues involved in the CrhR-RNA interaction, with C371 being critically important. Thus, the expression of a type III-Dv CRISPR-Cas system is linked to the redox status of the photosynthetic cell at the transcriptional and post-transcriptional levels.
