Open AccessThe CRISPR/Cas Immune System Is an Operon Regulated by LeuO, H-NS, and Leucine-Responsive Regulatory Protein in Salmonella enterica Serovar Typhi
Author(s) -
Liliana Medina-Aparicio,
Javier E Rebollar-Flores,
Ana L. Gallego-Hernández,
Arturo Pérez Vázquez,
Leticia Olvera,
Rosa-Maria Gutierrez-Rios,
Edmundo Calva,
Ismael Hernández-Lucas
Publication year - 2011
Publication title -
journal of bacteriology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.652
H-Index - 246
eISSN - 1067-8832
pISSN - 0021-9193
DOI - 10.1128/jb.01480-10
Subject(s) - biology , crispr , operon , salmonella typhi , crispr interference , salmonella enterica , genetics , transcriptional regulation , computational biology , bacteria , microbiology and biotechnology , salmonella , gene , cas9 , transcription factor , escherichia coli
Prokaryotes have developed multiple strategies to survive phage attack and invasive DNA. Recently, a novel genetic program denominated the CRISPR/Cas system was demonstrated to have a role in these biological processes providing genetic immunity. This defense mechanism is widespread in theArchaea andBacteria , suggesting an ancient origin. In the last few years, progress has been made regarding the functionality of the CRISPR/Cas system; however, many basic aspects of the system remain unknown. For instance, there are few studies about the conditions and regulators involved in its transcriptional control. In this work, we analyzed the transcriptional organization of the CRISPR/Cas system as well as the positive and negative regulators involved in its genetic expression inSalmonella enterica serovar Typhi. The results obtained show that inS . Typhi the CRISPR/Cas system is a LeuO-dependent operon silenced by the global regulator LRP, in addition to the previously known nucleoid-associated protein H-NS; both LRP and H-NS bind upstream and downstream of the transcriptional start site ofcasA. In this study, relevant nucleotides of thecasA regulatory region that mediate its LeuO transcriptional activation were identified. Interestingly, specific growth conditions (N-minimal medium) were found for the LeuO-independent expression of the CRISPR/Cas system inS . Typhi. Thus, our work provides evidence that there are multiple modulators involved in the genetic expression of this immune system inS . Typhi IMSS-1.