CRP represses the CRISPR/Cas system in Escherichia coli: evidence that endogenous CRISPR spacers impede phage P1 replication.
The CRISPR/Cas system is an important aspect in bacterial immunology. The anti-phage activity of the CRISPR system has been established using synthetic CRISPR spacers, but in vivo studies of endogenous CRISPR spacers are relatively scarce. Here, we showed that bacteriophage P1 titre in Escherichia coli decreased in the glucose-containing medium compared with that in the absence of glucose. This glucose effect of E. coli against phage P1 infection disappeared in cse3 deletion mutants. The effect on the susceptibility to phage P1 was associated with cAMP receptor protein (CRP)-mediated repression of cas genes transcription and crRNA maturation. Analysis of the regulatory element in the cse1 promoter region revealed a novel CRP binding site, which overlapped with a LeuO binding site. Furthermore, the limited sequence identity between endogenous spacers and the phage P1 genome was necessary and sufficient for CRISPR-mediated repression of phage P1 replication. Trans-expression of the third and seventh spacers in the CRISPR I region or third and sixth spacers in the CRISPR II region effectively reduced phage P1 titres in the CRISPR deletion mutants. These results demonstrate a novel regulatory mechanism for cas repression by CRP and provide evidence that endogenous spacers can repress phage P1 replication in E. coli.
Department of Biological Science and Technology, National Chiao Tung University, Hsin-Chu, 300, Taiwan.
Chi-Dung
CD
Yang
Yen-Hua
YH
Chen
Hsi-Yuan
HY
Huang
Hsien-Da
HD
Huang
Ching-Ping
CP
Tseng
D017101:Bacteriophage P1 / Q000502:physiology*; D064113:CRISPR-Cas Systems / Q000235:genetics / Q000502:physiology*; D002373:Cyclic AMP Receptor Protein / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism* / Q000821:virology; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics / Q000502:physiology; D014779:Virus Replication
D002373:Cyclic AMP Receptor Protein; D029968:Escherichia coli Proteins; C481662:crp protein, E coli