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Role of extracytoplasmic function sigma factor PG 1660 (RpoE) in the oxidative stress resistance regulatory network of Porphyromonas gingivalis
Author(s) -
Dou Y.,
Rutanhira H.,
Chen X.,
Mishra A.,
Wang C.,
Fletcher H.M.
Publication year - 2018
Publication title -
molecular oral microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 77
eISSN - 2041-1014
pISSN - 2041-1006
DOI - 10.1111/omi.12204
Subject(s) - porphyromonas gingivalis , sigma factor , mutant , gene , biology , virulence , promoter , transcription factor , microbiology and biotechnology , gene expression , chemistry , biochemistry , genetics , bacteria
Summary In Porphyromonas gingivalis , the protein PG 1660, composed of 174 amino acids, is annotated as an extracytoplasmic function ( ECF ) sigma factor (RpoE homologue‐σ24). Because PG 1660 can modulate several virulence factors and responds to environmental signals in P. gingivalis , its genetic properties were evaluated. PG 1660 is co‐transcribed with its downstream gene PG 1659 , and the transcription start site was identified as adenine residue 54‐nucleotides upstream of the ATG translation start codon. In addition to binding its own promoter, using the purified rPG 1660 and RNAP core enzyme from Escherichia coli with the PG 1660 promoter DNA as template, the function of PG 1660 as a sigma factor was demonstrated in an in vitro transcription assay. Transcriptome analyses of a P. gingivalis PG 1660 ‐defective isogenic mutant revealed that under oxidative stress conditions 176 genes including genes involved in secondary metabolism were downregulated more than two‐fold compared with the parental strain. The rPG 1660 protein also showed the ability to bind to the promoters of the highly downregulated genes in the PG 1660 ‐deficient mutant. As the ECF sigma factor PG 0162 has a 29% identity with PG 1660 and can modulate its expression, the cross‐talk between their regulatory networks was explored. The expression profile of the PG 0162 PG 1660 ‐deficient mutant ( P. gingivalis FLL 356) revealed that the type IX secretion system genes and several virulence genes were downregulated under hydrogen peroxide stress conditions. Taken together, we have confirmed that PG 1660 can function as a sigma factor, and plays an important regulatory role in the oxidative stress and virulence regulatory network of P. gingivalis .