trans-translation system is important for maintaining genome integrity during DNA damage in bacteria.

DNA integrity in bacteria is regulated by various factors that act on the DNA. trans-translation has previously been shown to be important for the survival of Escherichia coli cells exposed to certain DNA-damaging agents. However, the mechanisms underlying this sensitivity are poorly understood.

Mycobacterium leprae hsp18 promoter-EGFP transcriptional fusion construct: Environmental stress and strain-specific expression.

The Hsp18 protein is a major T-cell antigen of Mycobacterium leprae belonging to the family of small heat-shock proteins. The protein is specifically regulated at post-translational level during the intracellular growth of M. leprae within macrophages due to auto-phosphorylation, indicating its importance in the survival of the bacterium.

Horizontal transfer of domains in ssrA gene among Enterobacteriaceae.

The tmRNA (transfer messenger RNA), encoded by ssrA gene, is involved in rescuing of stalled ribosomes by a process called trans-translation. Additionally, regions of the ssrA gene (coding for tmRNA) were reported to serve as integration sites for various bacteriophages. Though variations in ssrA genes were reported, their functional relevance is less studied.

Two new mutations in dnaJ suppress DNA damage hypersensitivity and capsule overproduction phenotypes of Δlon mutant of Escherichia coli by modulating the expression of clpYQ (hslUV) and rcsA genes.

Lon is a major ATP-dependent protease of E. coli involved in degradation of abnormal misfolded proteins and specific regulatory proteins. Absence of Lon in E.

Unveiling the molecular basis for pleiotropy in selected rif mutants of Escherichia coli: Possible role for Tyrosine in the Rif binding pocket and fast movement of RNA polymerase.

Rifampicin (RIF) is still a first line of antibiotic in the treatment of bacterial diseases, in particular the Mycobacterial infections. The antimicrobial activity of RIF is attributed to its ability to inhibit transcription by binding to the β subunit of bacterial RNA polymerase (encoded by rpoB). Continued use of this drug resulted in the emergence of RIF resistant rpoB mutations in a high frequency that compels the use of RIF almost exclusively in drug combinations.

Suppression of Δlon phenotypes in Escherichia coli by N-terminal DnaK peptides.

Δlon mutant of Escherichia coli becomes hypersensitive to DNA damaging agents and over-produce capsule due to stabilization of the Lon substrates, namely, SulA and RcsA, respectively. These phenotypes were earlier found to be suppressed in Δlon ssrA::cat/pUC4 K and Δlon faa (DnaJ, G232D) strains, called as "Alp" strains. We observed that a plasmid carrying an E.

Microarray based transcriptome profile data of ∆ and ∆ strains of .

The data presented in this article shows the microarray based transcriptome profiles of ∆ and ∆ strains of . The mutation namely, was isolated spontaneously in the background of ∆ strain (over-produces colanic acid capsular polysaccharide) as a suppressor for over-production of colanic acid capsular polysaccharide (Meenakshi and Munavar, 2015) [1]. The strains were grown in LB medium at 30 °C overnight in duplicates.

A putative curved DNA region upstream of in plays a key role in transcriptional regulation by H-NS.

It is well established that in , the histone-like nucleoid structuring (H-NS) protein also functions as negative regulator of transcription. However, the exact mode of regulation of transcription by H-NS has not been studied extensively. Here, we report the multicopy effect of dominant-negative alleles on the transcription of based on expression of transcriptional fusion in ∆, ∆, ∆ and strains.

Evidence for up and down regulation of 450 genes by rpoB12 (rif) mutation and their implications in complexity of transcription modulation in Escherichia coli.

Analyses of mutations in rpoB subunit of Escherichia coli that lead to resistance to rifampicin have been invaluable in providing insight into events during transcription continue to be discovered. Earlier we reported that rpoB12 suppresses over-expression of cps genes in Δlon mutant of E. coli, by interfering with the transcription of rcsA.

Glu of PheT plays a pivotal role in the thermal stability of Escherichia coli PheRS enzyme.

As of date the two temperature sensitive mutations isolated in pheST operon include pheS5 (G →A ) and pheT354. Recently, we reported that G of pheS defines a hot spot for intragenic suppressors of pheS5. In this investigation, in 13 independent experiments, a collection of temperature sensitive mutants were isolated by localized mutagenesis.

Ascribing a novel role for tmRNA of Escherichia coli in resistance to mitomycin C.

Aim: The ssrA mutants were found to be more sensitive to mitomycin C (MMC) and our aim was to study this phenomenon in detail.

Materials & Methods: Strains were constructed by P1 transduction. pssrA plasmid was constructed by PCR-based cloning and transformation was done by CaCl method.

Suppression of capsule expression in Δlon strains of Escherichia coli by two novel rpoB mutations in concert with HNS: possible role for DNA bending at rcsA promoter.

Analyses of mutations in genes coding for subunits of RNA polymerase always throw more light on the intricate events that regulate the expression of gene(s). Lon protease of Escherichia coli is implicated in the turnover of RcsA (positive regulator of genes involved in capsular polysaccharide synthesis) and SulA (cell division inhibitor induced upon DNA damage). Failure to degrade RcsA and SulA makes lon mutant cells to overproduce capsular polysaccharides and to become sensitive to DNA damaging agents.

G673 could be a novel mutational hot spot for intragenic suppressors of pheS5 lesion in Escherichia coli.

The pheS5 Ts mutant of Escherichia coli defined by a G293 → A293 transition, which is responsible for thermosensitive Phenylalanyl-tRNA synthetase has been well studied at both biochemical and molecular level but genetic analyses pertaining to suppressors of pheS5 were hard to come by. Here we have systematically analyzed a spectrum of Temperature-insensitive derivatives isolated from pheS5 Ts mutant and identified two intragenic suppressors affecting the same base pair coordinate G673 (pheS19 defines G673 → T673 ; Gly225 → Cys225 and pheS28 defines G673 → C673 ; Gly225 → Arg225). In fact in the third derivative, the intragenic suppressor originally named pheS43 (G673 → C673 transversion) is virtually same as pheS28.

Selective alleviation of Mitomycin C sensitivity in lexA3 strains of Escherichia coli demands allele specificity of rif-nal mutations: a pivotal role for rpoB87-gyrA87 mutations.

Very recently, we have reported about an unconventional mode of elicitation of Mitomycin C (MMC) specific resistance in lexA3 (SOS repair deficient) mutants due to a combination of Rif-Nal mutations (rpoB87-gyrA87). We have clearly shown that UvrB is mandatory for this unconventional MMC resistance in rpoB87-gyrA87-lexA3 strains and uvrB is expressed more even without DNA damage induction from its LexA dependent promoter despite the uncleavable LexA3 repressor. The rpoB87 allele is same as the rpoB3595 which is known to give rise to a fast moving RNA Polymerase and gyrA87 is a hitherto unreported Nal(R) allele.

Evidence for involvement of UvrB in elicitation of 'SIR' phenotype by rpoB87-gyrA87 mutations in lexA3 mutant of Escherichia coli.

An unconventional DNA repair termed SIR (SOS Independent Repair), specific to mitomycin C (MMC) damage elicited by a combination of specific Rif(R) (rpoB87) and Nal(R) (gyrA87) mutations in SOS un-inducible strains of Escherichia coli was reported by Kumaresan and Jayaraman (1988). We report here that the rpoB87 mutation defines a C(1565)→T(1565) transition changing S(522)→F(522) and gyrA87 defines a G(244)→A(244) transition changing D(82)→N(82). The reconstructed lexA3 rpoB87 gyrA87 strain (DM49RN) exhibited resistance to MMC but not to UV as expected.

Evidence that the supE44 mutation of Escherichia coli is an amber suppressor allele of glnX and that it also suppresses ochre and opal nonsense mutations.

Translational readthrough of nonsense codons is seen not only in organisms possessing one or more tRNA suppressors but also in strains lacking suppressors. Amber suppressor tRNAs have been reported to suppress only amber nonsense mutations, unlike ochre suppressors, which can suppress both amber and ochre mutations, essentially due to wobble base pairing. In an Escherichia coli strain carrying the lacZU118 episome (an ochre mutation in the lacZ gene) and harboring the supE44 allele, suppression of the ochre mutation was observed after 7 days of incubation.

Allele-specific suppression of the temperature sensitivity of fitA/fitB mutants of Escherichia coli by a new mutation (fitC4): isolation, characterization and its implications in transcription control.

The temperature sensitive transcription defective mutant of Escherichia coli originally called fitA76 has been shown to harbour two missense mutations namely pheS5 and fit95. In order to obtain a suppressor of fitA76, possibly mapping in rpoD locus, a Ts+ derivative (JV4) was isolated from a fitA76 mutant. It was found that JV4 neither harbours the lesions present in the original fitA76 nor a suppressor that maps in or near rpoD.

Analysis of the Escherichia coli Alp phenotype: heat shock induction in ssrA mutants.

The major phenotypes of lon mutations, UV sensitivity and overproduction of capsule, are due to the stabilization of two substrates, SulA and RcsA. Inactivation of transfer mRNA (tmRNA) (encoded by ssrA), coupled with a multicopy kanamycin resistance determinant, suppressed both lon phenotypes and restored the rapid degradation of SulA. This novel protease activity was named Alp but was never identified further.