The noncoding RNA CcnA modulates the master cell cycle regulators CtrA and GcrA in Caulobacter crescentus

Bacteria are powerful models for understanding how cells divide and accomplish global regulatory programs. In Caulobacter crescentus, a cascade of essential master regulators supervises the correct and sequential activation of DNA replication, cell division, and development of different cell types. Among them, the response regulator CtrA plays a crucial role coordinating all those functions. Here, for the first time, we describe the role of a novel factor named CcnA (cell cycle noncoding RNA A), a cell cycle–regulated noncoding RNA (ncRNA) located at the origin of replication, presumably activated by CtrA, and responsible for the accumulation of CtrA itself. In addition, CcnA may be also involved in the inhibition of translation of the S-phase regulator, GcrA, by interacting with its 5′ untranslated region (5′ UTR). Performing in vitro experiments and mutagenesis, we propose a mechanism of action of CcnA based on liberation (ctrA) or sequestration (gcrA) of their ribosome-binding site (RBS). Finally, its role may be conserved in other alphaproteobacterial species, such as Sinorhizobium meliloti, representing indeed a potentially conserved process modulating cell cycle in Caulobacterales and Rhizobiales.

During cell cycle progression in the bacterium Caulobacter crescentus, the master cell cycle regulator CtrA is controlled by CcnA, a cell cycle-regulated non-coding RNA transcribed from a gene located at the origin of replication.     

Endocrine effects of psychological stress associated with neurobehavioral performance testing

Twenty-four healthy subjects were submitted to a computer-based performance evaluation system. The set of tests required sustained attention, and the last test was expressly designed to cause a moderate, acute psychological stress. Compared to baseline levels, both serum ACTH and beta-endorphins were increased after psychological testing in all subjects. Serum prolactin showed a slight and statistically nonsignificant decrease compared to baseline values. These results question the belief that psychological stress stimulates prolactin secretion, whereas it suggests that serum ACTH and beta-endorphins are reliable indicators of acute psychological stress.     

The RES domain toxins of RES‐Xre toxin‐antitoxin modules induce cell stasis by degrading NAD+

Type II toxin‐antitoxin (TA) modules, which are important cellular regulators in prokaryotes, usually encode two proteins, a toxin that inhibits cell growth and a nontoxic and labile inhibitor (antitoxin) that binds to and neutralizes the toxin. Here, we demonstrate that the res‐xre locus from Photorhabdus luminescens and other bacterial species function as bona fide TA modules in Escherichia coli. The 2.2 Å crystal structure of the intact Pseudomonas putida RES‐Xre TA complex reveals an unusual 2:4 stoichiometry in which a central RES toxin dimer binds two Xre antitoxin dimers. The antitoxin dimers each expose two helix‐turn‐helix DNA‐binding domains of the Cro repressor type, suggesting the TA complex is capable of binding the upstream promoter sequence on DNA. The toxin core domain shows structural similarity to ADP‐ribosylating enzymes such as diphtheria toxin but has an atypical NAD⁺‐binding pocket suggesting an alternative function. We show that activation of the toxin in vivo causes a depletion of intracellular NAD⁺ levels eventually leading to inhibition of cell growth in E. coli and inhibition of global macromolecular biosynthesis. Both structure and activity are unprecedented among bacterial TA systems, suggesting the functional scope of bacterial TA toxins is much wider than previously appreciated.     

Lung Fibroblasts Share Mesenchymal Stem Cell Features Which Are Altered in Chronic Obstructive Pulmonary Disease via the Overactivation of the Hedgehog Signaling Pathway

Background

Alteration of functional regenerative properties of parenchymal lung fibroblasts is widely proposed as a pathogenic mechanism for chronic obstructive pulmonary disease (COPD). However, what these functions are and how they are impaired in COPD remain poorly understood. Apart from the role of fibroblasts in producing extracellular matrix, recent studies in organs different from the lung suggest that such cells might contribute to repair processes by acting like mesenchymal stem cells. In addition, several reports sustain that the Hedgehog pathway is altered in COPD patients thus aggravating the disease. Nevertheless, whether this pathway is dysregulated in COPD fibroblasts remains unknown.

Objectives and Methods

We investigated the stem cell features and the expression of Hedgehog components in human lung fibroblasts isolated from histologically-normal parenchymal tissue from 25 patients—8 non-smokers/non-COPD, 8 smokers-non COPD and 9 smokers with COPD—who were undergoing surgery for lung tumor resection.

Results

We found that lung fibroblasts resemble mesenchymal stem cells in terms of cell surface marker expression, differentiation ability and immunosuppressive potential and that these properties were altered in lung fibroblasts from smokers and even more in COPD patients. Furthermore, we showed that some of these phenotypic changes can be explained by an over activation of the Hedgehog signaling in smoker and COPD fibroblasts.

Conclusions

Our study reveals that lung fibroblasts possess mesenchymal stem cell-features which are impaired in COPD via the contribution of an abnormal Hedgehog signaling. These processes should constitute a novel pathomechanism accounting for disease occurrence and progression.     

A mini review on molecularly imprinted polymer based halloysite nanotubes composites: innovative materials for analytical and environmental applications

Reviews in Environmental Science and Bio/Technology - Halloysite nanotubes (HNTs) are of importance for the elimination of various kinds of molecules from complex matrix due to their outstanding...     

Robustness assessment of whole bacterial genome segmentations

Comparison of closely related bacterial genomes has revealed the presence of highly conserved sequences forming a "backbone" that is interrupted by numerous, less conserved, DNA fragments. Segmentation of bacterial genomes into backbone and variable regions is particularly useful to investigate, among other things, bacterial genome evolution. Several software tools have been designed to compare complete bacterial chromosomes and a few online databases store pre-computed genome comparisons. However, very few statistical methods are available to evaluate the reliability of these software tools and to compare the results obtained with them. To fill this gap, we have developed two local scores to measure the robustness of bacterial genome segmentations. Our method uses a simulation procedure based on random perturbations of the compared genomes. The two scores described in this article provide useful information and are easy to implement, and their interpretation is intuitive. We show that they are suited to discriminate between robust and non-robust segmentations when genome aligners such as MAUVE and MGA are used.     

External forces control mitotic spindle positioning

The response of cells to forces is essential for tissue morphogenesis and homeostasis. This response has been extensively investigated in interphase cells, but it remains unclear how forces affect dividing cells. We used a combination of micro-manipulation tools on human dividing cells to address the role of physical parameters of the micro-environment in controlling the cell division axis, a key element of tissue morphogenesis. We found that forces applied on the cell body direct spindle orientation during mitosis. We further show that external constraints induce a polarization of dynamic subcortical actin structures that correlate with spindle movements. We propose that cells divide according to cues provided by their mechanical micro-environment, aligning daughter cells with the external force field.     

Broad-spectrum biofilm inhibition by Kingella kingae exopolysaccharide

Cell-free extracts prepared from Kingella kingae colony biofilms were found to inhibit biofilm formation by Aggregatibacter actinomycetemcomitans, Klebsiella pneumoniae, Staphylococcus aureus, Staphylococcus epidermidis, Candida albicans, and K. kingae. The extracts evidently inhibited biofilm formation by modifying the physicochemical properties of the cell surface, the biofilm matrix, and the substrate. Chemical and biochemical analyses indicated that the biofilm inhibition activity in the K. kingae extract was due to polysaccharide. Structural analyses showed that the extract contained two major polysaccharides. One was a linear polysaccharide with the structure →6)-α-d-GlcNAcp-(1→5)-β-d-OclAp-(2→, which was identical to a capsular polysaccharide produced by Actinobacillus pleuropneumoniae serotype 5. The second was a novel linear polysaccharide, designated PAM galactan, with the structure →3)-β-d-Galf-(1→6)-β-d-Galf-(1→. Purified PAM galactan exhibited broad-spectrum biofilm inhibition activity. A cluster of three K. kingae genes encoding UDP-galactopyranose mutase (ugm) and two putative galactofuranosyl transferases was sufficient for the synthesis of PAM galactan in Escherichia coli. PAM galactan is one of a growing number of bacterial polysaccharides that exhibit antibiofilm activity. The biological roles and potential technological applications of these molecules remain unknown.     

Genome size and cytogenetic characterization of three Algerian Retama species

Thirty-three populations belonging to the three Retama species, Retama monosperma, Retama raetam and Retama sphaerocarpa, were collected to study species differentiation using flow cytometry for 2C DNA assessment and molecular cytogenetics for karyotype organisation. All were 2n = 48. Genome size ranged from 1.76 to 1.97 pg and revealed significant intraspecific variation correlated to the geographic distribution of the populations. The number and position of the two ribosomal gene families 5S and 45S were determined by fluorescent in situ hybridization, revealing chromosome reorganisation between species. In R. raetam and R. monosperma, the minor 5S loci co-localised with 45S on the satellite chromosome pair. Fluorochrome banding identified GC- and AT-rich DNA regions. In R. monosperma a unique chromomycin positive GC-rich band was observed associated with the secondary constriction. In contrast, an original pattern showing two chromomycin positive bands localised at each side of the extended rDNA locus was observed in R. sphaerocarpa and R. raetam. The polymorphism revealed in our cytogenetic data allowed us to separate the group of R. raetam and R. monosperma from R. sphaerocarpa.