Direct observation of a crescent-shape chromosome in expanded Bacillus subtilis cells.

Bacterial chromosomes are folded into tightly regulated three-dimensional structures to ensure proper transcription, replication, and segregation of the genetic information. Direct visualization of chromosomal shape within bacterial cells is hampered by cell-wall confinement and the optical diffraction limit. Here, we combine cell-shape manipulation strategies, high-resolution fluorescence microscopy techniques, and genetic engineering to visualize the shape of unconfined bacterial chromosome in real-time in live Bacillus subtilis cells that are expanded in volume.

A conserved antigen induces respiratory Th17-mediated broad serotype protection against pneumococcal superinfection.

Several vaccines targeting bacterial pathogens show reduced efficacy upon concurrent viral infection, indicating that a new vaccinology approach is required. To identify antigens for the human pathogen Streptococcus pneumoniae that are effective following influenza infection, we performed CRISPRi-seq in a murine model of superinfection and identified the conserved lafB gene as crucial for virulence. We show that LafB is a membrane-associated, intracellular protein that catalyzes the formation of galactosyl-glucosyl-diacylglycerol, a glycolipid important for cell wall homeostasis.

When cell death goes wrong: inflammatory outcomes of failed apoptosis and mitotic cell death.

Apoptosis is a regulated cellular pathway that ensures that a cell dies in a structured fashion to prevent negative consequences for the tissue or the organism. Dysfunctional apoptosis is a hallmark of numerous pathologies, and treatments for various diseases are successful based on the induction of apoptosis. Under homeostatic conditions, apoptosis is a non-inflammatory event, as the activation of caspases ensures that inflammatory pathways are disabled.

A joint-ParB interface promotes Smc DNA recruitment.

Chromosomes readily unlink and segregate to daughter cells during cell division, highlighting a remarkable ability of cells to organize long DNA molecules. SMC complexes promote DNA organization by loop extrusion. In most bacteria, chromosome folding initiates at dedicated start sites marked by the ParB/parS partition complexes.

Increased apoptotic sensitivity of glioblastoma enables therapeutic targeting by BH3-mimetics.

Glioblastoma (GBM) is the most prevalent malignant primary brain tumour in adults. GBM typically has a poor prognosis, mainly due to a lack of effective treatment options leading to tumour persistence or recurrence. We investigated the therapeutic potential of targeting anti-apoptotic BCL-2 proteins in GBM.

Relief of ParB autoinhibition by DNA catalysis and recycling of ParB by CTP hydrolysis promote bacterial centromere assembly.

Three-component ParABS systems are widely distributed factors for plasmid partitioning and chromosome segregation in bacteria. ParB acts as adaptor protein between the 16–base pair centromeric DNA sequences and the DNA segregation proteins ParA and Smc (structural maintenance of chromosomes). Upon cytidine triphosphate (CTP) and DNA binding, ParB dimers form DNA clamps that spread onto -flanking DNA by sliding, thus assembling the so-called partition complex.

A low Smc flux avoids collisions and facilitates chromosome organization in .

SMC complexes are widely conserved ATP-powered DNA-loop-extrusion motors indispensable for organizing and faithfully segregating chromosomes. How SMC complexes translocate along DNA for loop extrusion and what happens when two complexes meet on the same DNA molecule is largely unknown. Revealing the origins and the consequences of SMC encounters is crucial for understanding the folding process not only of bacterial, but also of eukaryotic chromosomes.

Self-organization of centromeres by the ParB CTP hydrolase.

ParABS systems facilitate chromosome segregation and plasmid partitioning in bacteria and archaea. ParB protein binds centromeric DNA sequences and spreads to flanking DNA. We show that ParB is an enzyme that hydrolyzes cytidine triphosphate (CTP) to cytidine diphosphate (CDP).

Mitochondria as multifaceted regulators of cell death.

Through their many and varied metabolic functions, mitochondria power life. Paradoxically, mitochondria also have a central role in apoptotic cell death. Upon induction of mitochondrial apoptosis, mitochondrial outer membrane permeabilization (MOMP) usually commits a cell to die.

BAX/BAK-Induced Apoptosis Results in Caspase-8-Dependent IL-1β Maturation in Macrophages.

IL-1β is a cytokine of pivotal importance to the orchestration of inflammatory responses. Synthesized as an inactive pro-cytokine, IL-1β requires proteolytic maturation to gain biological activity. Here, we identify intrinsic apoptosis as a non-canonical trigger of IL-1β maturation.

Identifying Target RNAs of PARPs.

Posttranscriptional regulation of RNA is an important component of gene expression by controlling the total amount of mRNA available for translation into protein. It involves multiple pathways including nuclear processing of mRNA and its precursors, RNA silencing, and regulation of RNA decay. Poly(ADP-ribose) polymerases (PARPs), enzymes that modify target proteins with ADP-ribose, play important roles in several RNA-regulatory pathways.

Structure of Full-Length SMC and Rearrangements Required for Chromosome Organization.

Multi-subunit SMC complexes control chromosome superstructure and promote chromosome disjunction, conceivably by actively translocating along DNA double helices. SMC subunits comprise an ABC ATPase "head" and a "hinge" dimerization domain connected by a 49 nm coiled-coil "arm." The heads undergo ATP-dependent engagement and disengagement to drive SMC action on the chromosome.

Tight Sequestration of BH3 Proteins by BCL-xL at Subcellular Membranes Contributes to Apoptotic Resistance.

Anti-apoptotic BCL-2 family members bind to BH3-only proteins and multidomain BAX/BAK to preserve mitochondrial integrity and maintain survival. Whereas inhibition of these interactions is the biological basis of BH3-mimetic anti-cancer therapy, the actual response of membrane-bound protein complexes to these compounds is currently ill-defined. Here, we find that treatment with BH3 mimetics targeting BCL-xL spares subsets of cells with the highest levels of this protein.

New directions in poly(ADP-ribose) polymerase biology.

Poly(ADP-ribose) polymerases (PARPs) regulate the function of target proteins by modifying them with ADP-ribose, a large and unique post-translational modification. Humans express 17 PARPs; however, historically, much of the focus has been on PARP1 and its function in DNA damage repair. Recent work has uncovered an amazing diversity of function for these enzymes including the regulation of fundamental physiological processes in the cell and at the organismal level, as well as new roles in regulating cellular stress responses.

RNA Regulation by Poly(ADP-Ribose) Polymerases.

Posttranscriptional regulation of RNA facilitates the fine-tuning of gene expression. It occurs through multiple pathways that include the nuclear processing of mRNA and its precursors, mRNA silencing, regulation of mRNA decay, and regulation of translation. Poly(ADP-ribose) polymerases (PARPs), enzymes that modify target proteins with ADP-ribose, play important roles in many of the RNA regulatory pathways through multiple mechanisms.

Macrophage activation: on par with LPS.

The inflammatory response is a critical component of the immune system that is activated by stimuli such as cytokines, foreign DNA, RNA, or other harmful substances. Krukenberg et al. (2015) identify poly(ADP-ribose) as a new signaling molecule that activates inflammation, thus providing yet another mechanism by which PARPs are involved in cellular stress responses.

Poly(ADP-ribose) polymerase-13 and RNA regulation in immunity and cancer.

Post-transcriptional regulation of RNA is an important mechanism for activating and resolving cellular stress responses. Poly(ADP-ribose) polymerase-13 (PARP13), also known as ZC3HAV1 and zinc-finger antiviral protein (ZAP), is an RNA-binding protein that regulates the stability and translation of specific mRNAs, and modulates the miRNA silencing pathway to globally affect miRNA targets. These functions of PARP13 are important components of the cellular response to stress.