A paper on the effect of a transcription terminator on transcription silencing 

In a paper, just published in The Journal of Biosciences, we use genomic techniques to show that inhibition of transcription terminator Rho abrogates the binding of the transcription silencer H-NS to the E. coli chromosome. This work helps rationalise recent findings from various labs, which have observed similarities in the effects of Rho and H-NS on E. coli gene expression. The experimental work was performed by Deepti Chandraprakash.

The abstract reads as follows:

Many horizontally acquired genes (xenogenes) in the bacterium Escherichia coli are maintained in a silent transcriptional state by the nucleoid-associated transcription regulatory protein H-NS. Recent evidence has shown that antibiotic-mediated inhibition of the transcription terminator protein Rho leads to de-repression of horizontally acquired genes, akin to a deletion of hns. The mechanism behind this similarity in outcomes between the perturbations of two distinct processes remains unclear. Using ChIP-seq of H-NS in wild-type cells, in addition to that in cells treated with bicyclomycin - a specific inhibitor of Rho, we show that bicyclomycin treatment leads to a decrease in binding signal for H-NS to the E. coli chromosome. Rho inhibition leads to RNA polymerase readthrough, which in principle could displace H-NS from the DNA, thus leading to transcriptional derepression of H-NS-silenced genes. Other possible mediators of the effect of Rho on H-NS are discussed. A possible positive feedback between Rho and H-NS might help reinforce xenogene silencing. 

We are funded by NCBS (DAE), DST, CSIR, DBT. and UGC