The CnuK9E H-NS Complex Antagonizes DNA Binding of DicA and Leads to Temperature-Dependent Filamentous Growth in E. coli

Abstract

Cnu (an OriC-binding nucleoid protein) associates with H-NS. A variant of Cnu was identified as a key factor for filamentous growth of a wild-type Escherichia coli strain at 37°C. This variant (CnuK9E) bears a substitution of a lysine to glutamic acid, causing a charge reversal in the first helix. The temperature-dependent filamentous growth of E. coli bearing CnuK9E could be reversed by either lowering the temperature to 25°C or lowering the CnuK9E concentration in the cell. Gene expression analysis suggested that downregulation of dicA by CnuK9E causes a burst of dicB transcription, which, in turn, elicits filamentous growth. In vivo assays indicated that DicA transcriptionally activates its own gene, by binding to its operator in a temperature-dependent manner. The antagonizing effect of CnuK9E with H-NS on DNA-binding activity of DicA was stronger at 37°C, presumably due to the lower operator binding of DicA at 37°C. These data suggest that the temperature-dependent negative effect of CnuK9E on DicA binding plays a major role in filamentous growth. The C-terminus of DicA shows significant amino acid sequence similarity to the DNA-binding domains of RovA and SlyA, regulators of pathogenic genes in Yersinia and Salmonella, respectively, which also show better DNA-binding activity at 25°C.

The Association of Cell Division Regulated by DicC With the Formation of Viable but Non-culturable Escherichia coli O157:H7

“…A previous study indicated that DicA can inhibit the transcription of the dicB gene (Béjar et al, 1988). In addition, recent advances indicated that downregulation of the dicA gene by CnuK9E, a mutant of the OriC-binding nucleoid protein (Cnu), could induce a burst of dicB expression and inhibit cell division (Yun et al, 2012). In this study, we found that overexpression of the dicA gene resulted in an increase in the cell growth rate, implying that the expression levels of dicB decreased and cell division was suppressed, which is consistent with previous studies.…”

“…DicC and DicA have been shown to regulate cell division in bacteria, suggesting that these genes can affect the bacterial growth rate (Béjar and Bouché, 1985;Béjar et al, 1986;Yun et al, 2012). Therefore, the bacterial growth rates of the WT, dicC mutant and dicC/DicC complementary strains as well as the vector, DicC and DicA strains were tested.…”

“…It has been reported that DicC and DicA affect cell division and growth rate by regulating the expression of the dicB gene (Yun et al, 2012;Yang et al, 2016). Therefore, the expression of the dicB gene in the WT, mutant, vector and recombinant strains was determined by qPCR.…”

A Comparison of the Costs and Benefits of Bacterial Gene Expression

“…Of these twenty genes, five are induced by specific conditions that are not included in the mRNA expression compendium (allB, kilR, mngB, rhsD, and xapA; expression of kilR is induced by nalidixic acid stress (24)). Two more genes (dicB and dicC) are repressed by DicA (25) and their expression increases dramatically in a strain that has a regulatory mutation (26), but the natural signal that controls their expression is not known. Five other genes are functional when overexpressed and conditions that induce their expression are not known (acrE, htrE, ompN, rihB, and smfD).…”

Estudo dinâmico da expressão gênica global durante a interação STEC-enterócito utilizando séries temporais

“…em Yersinia e Salmonella, respectivamente (Yun et al, 2012). Estas duas proteínas regulam vários processos fisiológicos bacterianos envolvidos na sobrevivência e adaptação ao estresse ambiental e na virulência (Daniels et al, 1996;Tran et al, 2005;Ellison;Miller, 2006).…”