p21 maintains senescent cell viability under persistent DNA damage response by restraining JNK and caspase signaling

Cellular senescence is a permanent state of cell cycle arrest that protects the organism from tumorigenesis and regulates tissue integrity upon damage and during tissue remodeling. However, accumulation of senescent cells in tissues during aging contributes to age‐related pathologies. A deeper understanding of the mechanisms regulating the viability of senescent cells is therefore required. Here, we show that the CDK inhibitor p21 (CDKN1A) maintains the viability of DNA damage‐induced senescent cells. Upon p21 knockdown, senescent cells acquired multiple DNA lesions that activated ataxia telangiectasia mutated (ATM) and nuclear factor (NF)‐κB kinase, leading to decreased cell survival. NF‐κB activation induced TNF‐α secretion and JNK activation to mediate death of senescent cells in a caspase‐ and JNK‐dependent manner. Notably, p21 knockout in mice eliminated liver senescent stellate cells and alleviated liver fibrosis and collagen production. These findings define a novel pathway that regulates senescent cell viability and fibrosis.     

A Differential Effect of E. coli Toxin-Antitoxin Systems on Cell Death in Liquid Media and Biofilm Formation

Toxin-antitoxin (TA) modules are gene pairs specifying for a toxin and its antitoxin and are found on the chromosomes of many bacteria including pathogens. Here we report how each of five such TA systems in E. coli affect bacterial cell death differently in liquid media and during biofilm formation. Of all these systems, only the TA system mazEF mediated cell death both in liquid media and during biofilm formation. At the other extreme, as our results have revealed here, the TA system dinJ-YafQ is unique in that it is involved only in the death process during biofilm formation. Cell death governed by mazEF and dinJ-YafQ seems to participate in biofilm formation through a novel mechanism.     

Transfer-PCR (TPCR): a highway for DNA cloning and protein engineering

DNA cloning and protein engineering are basic methodologies employed for various applications in all life-science disciplines. Manipulations of DNA however, could be a lengthy process that slows down subsequent experiments. To facilitate both DNA cloning and protein engineering, we present Transfer-PCR (TPCR), a novel approach that integrates in a single tube, PCR amplification of the target DNA from an origin vector and its subsequent integration into the destination vector. TPCR can be applied for incorporation of DNA fragments into any desired position within a circular plasmid without the need for purification of the intermediate PCR product and without the use of any commercial kit. Using several examples, we demonstrate the applicability of the TPCR platform for both DNA cloning and for multiple-site targeted mutagenesis. In both cases, we show that the TPCR reaction is most efficient within a narrow range of primer concentrations. In mutagenesis, TPCR is primarily advantageous for generation of combinatorial libraries of targeted mutants but could be also applied to generation of variants with specific multiple mutations throughout the target gene. Adaptation of the TPCR platform should facilitate, simplify and significantly reduce time and costs for diverse protein structure and functional studies.     

Nest desertion by Grey Fantails during nest building in response to perceived predation risk

ABSTRACT Grey Fantails (Rhipidura albiscapa), a common Australian flycatcher, commonly desert their nests before egg‐laying. We tested the hypothesis that Grey Fantails desert incomplete nests in response to the attention of predators by placing a mounted Pied Currawong (Strepera graculina), a common nest predator, near fantail nests that were under construction. As a control, we placed a mounted King Parrot (Alisteris scapularis), a nonpredatory bird similar in size to Pied Currawongs, near other fantail nests. Four of six female fantails (67%) deserted incomplete nests in response to the presentation of the Pied Currawong. In contrast, none of the seven females presented with a mounted King Parrot deserted. Female Grey Fantails may use the attention of a predator at the nest during the building stage as a cue to desert. Such desertion may be adaptive for Grey Fantails because currawongs are large predators, making successful nest defense unlikely, and they also present considerable risk to adults. In addition, fantails may raise multiple broods during a breeding season and, therefore, have a high renesting potential.     

Isolation of myoinositol from solutions of enzymatic biotransformation

The transferase reaction between phospholipids and inositol catalyzed by phospholipase D on phase interface in water-organic solvent systems was studied. Optimal conditions for phosphatidylinositol synthesis in water-organic solvent heterogeneous system were determined. The rapid separation of the hydrophobic components, phospholipids, from water-soluble products, alcohols, was observed in the systems with organic solvents. Displacement of myo-inositol from phosphatidylinositol by methanol, alcohol substrate, added to the reaction medium was shown in hexane-water system. Myo-inositol was isolated from the mixture of its isomers by two-stage transferase reaction catalyzed by phospholipase D.     

The Hemodynamic Basis for Positional- and Inter-Fetal Dependent Effects in Dual Arterial Supply of Mouse Pregnancies

In mammalian pregnancy, maternal cardiovascular adaptations must match the requirements of the growing fetus(es), and respond to physiologic and pathologic conditions. Such adaptations are particularly demanding for mammals bearing large-litter pregnancies, with their inherent conflict between the interests of each individual fetus and the welfare of the entire progeny. The mouse is the most common animal model used to study development and genetics, as well as pregnancy-related diseases. Previous studies suggested that in mice, maternal blood flow to the placentas occurs via a single arterial uterine loop generated by arterial-arterial anastomosis of the uterine artery to the uterine branch of the ovarian artery, resulting in counter bi-directional blood flow. However, we provide here experimental evidence that each placenta is actually supplied by two distinct arterial inputs stemming from the uterine artery and from the uterine branch of the ovarian artery, with position-dependent contribution of flow from each source. Moreover, we report significant positional- and inter-fetal dependent alteration of placental perfusion, which were detected by in vivo MRI and fluorescence imaging. Maternal blood flow to the placentas was dependent on litter size and was attenuated for placentas located centrally along the uterine horn. Distinctive apposing, inter-fetal hemodynamic effects of either reduced or elevated maternal blood flow, were measured for placenta of normal fetuses that are positioned adjacent to either pathological, or to hypovascular Akt1-deficient placentas, respectively. The results reported here underscore the critical importance of confounding local and systemic in utero effects on phenotype presentation, in general and in the setting of genetically modified mice. The unique robustness and plasticity of the uterine vasculature architecture, as reported in this study, can explain the ability to accommodate varying litter sizes, sustain large-litter pregnancies and overcome pathologic challenges. Remarkably, the dual arterial supply is evolutionary conserved in mammals bearing a single offspring, including primates.