Transcription Elongation Factor GreA Plays a Key Role in Cellular Invasion and Virulence of Francisella tularensis subsp. novicida

Abstract

Francisella tularensis is a facultative intracellular Gram-negative bacterium that causes the zoonotic disease tularemia. We identified the transcription elongation factor GreA as a virulence factor in our previous study, but its role was not defined. Here, we investigate the effects of the inactivation of the greA gene, generating a greA mutant of F. tularensis subsp. novicida. Inactivation of greA impaired the bacterial invasion into and growth within host cells, and subsequently virulence in mouse infection model. A transcriptomic analysis (RNA-Seq) showed that the loss of GreA caused the differential expression of 196 bacterial genes, 77 of which were identified as virulence factors in previous studies. To confirm that GreA regulates the expression of virulence factors involved in cell invasion by Francisella, FTN_1186 (pepO) and FTN_1551 (ampD) gene mutants were generated. The ampD deletion mutant showed reduced invasiveness into host cells. These results strongly suggest that GreA plays an important role in the pathogenesis of Francisella by affecting the expression of virulence genes and provide new insights into the complex regulation of Francisella infection.

Involvement of Transcription Elongation Factor GreA in Mycobacterium Viability, Antibiotic Susceptibility, and Intracellular Fitness

“…It is known that GreA influences not only cellular invasion but also replication in Francisella tularensis subsp. Novicida (Cui et al, 2018) and Salmonella typhimurium (Gaviria-Cantin et al, 2017). Our data also revealed that greA deletion caused a slight reduction of intracellular fitness in M. tuberculosis H37Rv, suggesting that GreA is required for the maintenance of intracellular survival of M. tuberculosis.…”

Transcriptomic Analysis of Listeria monocytogenes in Response to Bile Under Aerobic and Anaerobic Conditions

“…In F. tularensis , GreA was found to be required for invasion and intracellular growth of bacteria. Cui et al (2018) also observed suppression of virulence of the greA mutant in mouse model. Transcriptomics analysis of the greA mutant revealed down-regulation of various genes responsible for virulence.…”

“…GreA has been found to have roles in affecting functions of virulence gene expression in the pathogen Francisella tularensis subsp. Novicida ( Cui et al, 2018 ). In F. tularensis , GreA was found to be required for invasion and intracellular growth of bacteria.…”

“…PrfA which regulates many virulence genes of L. monocytogenes has been shown to down-regulate ClpC production (Karatzas et al, 2003). Although Karatzas et al (2003) could not find any relationship between clp and prfA, there is still a possibility that there is a connection between the regulation of Clp by CtsR under anaerobic conditions in exposure to bile at acidic pH (Cui et al, 2018).…”

Relation of the pdxB-usg-truA-dedA Operon and the truA Gene to the Intracellular Survival of Salmonella enterica Serovar Typhimurium

“…To determine if the genes in the operon were co-transcribed, the intergenic regions of genes were amplified by RT-PCR [27]. The RNA of the parental strain was extracted and cDNA was synthesized by reverse transcription using the method descibed before.…”