RNA helicase-regulated processing of the operon results in differential cistron expression and accumulation of two sRNAs.

The arrangement of functionally-related genes in operons is a fundamental element of how genetic information is organized in prokaryotes. This organization ensures coordinated gene expression by co-transcription. Often, however, alternative genetic responses to specific stress conditions demand the discoordination of operon expression.

Replication stress checkpoint signaling controls tRNA gene transcription.

In budding yeast, the transcriptional machinery at tRNA genes naturally interferes with replication in a way that can promote chromosome breakage. Here we show that a signaling module composed of core components of the replication stress checkpoint pathway represses this fork-pausing machinery in normally cycling and genotoxin-treated cells. Specifically, the sensor kinase Mec1, the signaling adaptor Mrc1 and the transducer kinase Rad53 relay signals that globally repress tRNA gene transcription during unchallenged proliferation and under conditions of replication stress.

Salmonella and Enteropathogenic Escherichia coli Interactions with Host Cells: Signaling Pathways.

The host-pathogen interaction involves a myriad of initiations and responses from both sides. Bacterial pathogens such as enteropathogenic Escherichia coli (EPEC) and Salmonella enterica have numerous virulence factors that interact with and alter signaling components of the host cell to initiate responses that are beneficial to pathogen survival and persistence. The study of Salmonella and EPEC infection reveals intricate connections between host signal transduction, cytoskeletal architecture, membrane trafficking, and cytokine gene expression.

RNA structural rearrangement via unwinding and annealing by the cyanobacterial RNA helicase, CrhR.

Rearrangement of RNA secondary structure is crucial for numerous biological processes. RNA helicases participate in these rearrangements through the unwinding of duplex RNA. We report here that the redox-regulated cyanobacterial RNA helicase, CrhR, is a bona fide RNA helicase possessing both RNA-stimulated ATPase and bidirectional ATP-stimulated RNA helicase activity.

The Salmonella enterica serovar typhimurium divalent cation transport systems MntH and SitABCD are essential for virulence in an Nramp1G169 murine typhoid model.

Nramp1 is a transporter that pumps divalent cations from the vacuoles of phagocytic cells and is associated with the innate resistance of mice to diverse intracellular pathogens. We demonstrate that sitA and mntH, genes encoding high-affinity metal ion uptake systems in Salmonella enterica serovar Typhimurium, are upregulated when Salmonella is internalized by Nramp1-expressing macrophages and play an essential role in systemic infection of congenic Nramp1-expressing mice.

SseK1 and SseK2 are novel translocated proteins of Salmonella enterica serovar typhimurium.

Salmonella enterica is a gram-negative, facultative intracellular pathogen that causes disease symptoms ranging from gastroenteritis to typhoid fever. A key virulence strategy is the translocation of bacterial effector proteins into the host cell, mediated by the type III secretion systems (TTSSs) encoded in Salmonella pathogenicity island 1 (SPI-1) and SPI-2. In S.

Iron-regulated phenylalanyl-tRNA synthetase activity in Azotobacter vinelandii.

Azotobacter vinelandii strain UA22 was produced by pTn5luxAB mutagenesis, such that the promoterless luxAB genes were transcribed in an iron-repressible manner. Tn5luxAB was localized to a fragment of chromosomal DNA encoding the thrS, infC, rpmI, rplT, pheS and pheT genes, with Tn5 inserted in the 3'-end of pheS. The isolation of this mutation in an essential gene was possible because of polyploidy in Azotobacter, such that strain UA22 carried both wild-type and mutant alleles of pheS.