Optimization of norovirus virus‐like particle production in Pichia pastoris using a real‐time near‐infrared bioprocess monitor

The production of norovirus virus‐like particles (NoV VLPs) displaying NY‐ESO‐1 cancer testis antigen in Pichia pastoris BG11 Mut⁺ has been enhanced through feed‐strategy optimization using a near‐infrared bioprocess monitor (RTBio^® Bioprocess Monitor, ASL Analytical, Inc.), capable of monitoring and controlling the concentrations of glycerol and methanol in real‐time. The production of NoV VLPs displaying NY‐ESO‐1 in P. pastoris has potential as a novel cancer vaccine platform. Optimization of the growth conditions resulted in an almost two‐fold increase in the expression levels in the fermentation supernatant of P. pastoris as compared to the starting conditions. We investigated the effect of methanol concentration, batch phase time, and batch to induction transition on NoV VLP‐NY‐ESO‐1 production. The optimized process included a glycerol transition phase during the first 2 h of induction and a methanol concentration set point of 4 g L^?1 during induction. Utilizing the bioprocess monitor to control the glycerol and methanol concentrations during induction resulted in a maximum NoV VP1‐NY‐ESO‐1 yield of 0.85 g L^?1. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:518–526, 2016     

Site-Specific Cryo-focused Ion Beam Sample Preparation Guided by 3D Correlative Microscopy

The development of cryo-focused ion beam (cryo-FIB) for the thinning of frozen-hydrated biological specimens enabled cryo-electron tomography (cryo-ET) analysis in unperturbed cells and tissues. However, the volume represented within a typical FIB lamella constitutes a small fraction of the biological specimen. Retaining low-abundance and dynamic subcellular structures or macromolecular assemblies within such limited volumes requires precise targeting of the FIB milling process. In this study, we present the development of a cryo-stage allowing for spinning-disk confocal light microscopy at cryogenic temperatures and describe the incorporation of the new hardware into existing workflows for cellular sample preparation by cryo-FIB. Introduction of fiducial markers and subsequent computation of three-dimensional coordinate transformations provide correlation between light microscopy and scanning electron microscopy/FIB. The correlative approach is employed to guide the FIB milling process of vitrified cellular samples and to capture specific structures, namely fluorescently labeled lipid droplets, in lamellas that are 300 nm thick. The correlation procedure is then applied to localize the fluorescently labeled structures in the transmission electron microscopy image of the lamella. This approach can be employed to navigate the acquisition of cryo-ET data within FIB-lamellas at specific locations, unambiguously identified by fluorescence microscopy.     

Microbiome Composition and Function Drives Wound-Healing Impairment in the Female Genital Tract

The mechanism(s) by which bacterial communities impact susceptibility to infectious diseases, such as HIV, and maintain female genital tract (FGT) health are poorly understood. Evaluation of FGT bacteria has predominantly been limited to studies of species abundance, but not bacterial function. We therefore sought to examine the relationship of bacterial community composition and function with mucosal epithelial barrier health in the context of bacterial vaginosis (BV) using metaproteomic, metagenomic, and in vitro approaches. We found highly diverse bacterial communities dominated by Gardnerella vaginalis associated with host epithelial barrier disruption and enhanced immune activation, and low diversity communities dominated by Lactobacillus species that associated with lower Nugent scores, reduced pH, and expression of host mucosal proteins important for maintaining epithelial integrity. Importantly, proteomic signatures of disrupted epithelial integrity associated with G. vaginalis-dominated communities in the absence of clinical BV diagnosis. Because traditional clinical assessments did not capture this, it likely represents a larger underrepresented phenomenon in populations with high prevalence of G. vaginalis. We finally demonstrated that soluble products derived from G. vaginalis inhibited wound healing, while those derived from L. iners did not, providing insight into functional mechanisms by which FGT bacterial communities affect epithelial barrier integrity.     

Early‐onset aging and mitochondrial defects associated with loss of histone acetyltransferase 1 (Hat1)

Histone acetyltransferase 1 (Hat1) is responsible for the acetylation of newly synthesized histone H4 on lysines 5 and 12 during the process of chromatin assembly. To understand the broader biological role of Hat1, we have generated a conditional mouse knockout model of this enzyme. We previously reported that Hat1 is required for viability and important for mammalian development and genome stability. In this study, we show that haploinsufficiency of Hat1 results in a significant decrease in lifespan. Defects observed in Hat1^+/? mice are consistent with an early‐onset aging phenotype. These include lordokyphosis (hunchback), muscle atrophy, minor growth retardation, reduced subcutaneous fat, cancer, and paralysis. In addition, the expression of Hat1 is linked to the normal aging process as Hat1 mRNA and protein becomes undetectable in many tissues in old mice. At the cellular level, fibroblasts from Hat1 haploinsufficient embryos undergo early senescence and accumulate high levels of p21. Hat1^+/? mouse embryonic fibroblasts (MEFs) display modest increases in endogenous DNA damage but have significantly higher levels of reactive oxygen species (ROS). Consistently, further studies show that Hat1^?/? MEFs exhibit mitochondrial defects suggesting a critical role for Hat1 in mitochondrial function. Taken together, these data show that loss of Hat1 induces multiple hallmarks of early‐onset aging.     

Evolutionary replacement of components in a salamander pheromone signaling complex: more evidence for phenotypic-molecular decoupling

In this article we explore the evolutionary history of a functional complex at the molecular level in plethodontid salamanders. The complex consists of a proteinaceous courtship pheromone, a pheromone-producing gland on the male's chin, and a set of behaviors for delivering the pheromone to the female. Long-term evolutionary stasis is the defining feature of this complex at both the morphological and behavioral levels. However, our previous assessment of the pheromone gene, plethodontid receptivity factor (PRF), revealed rapid evolution at the molecular level despite stasis at higher levels of organization. Analysis of a second pheromone gene, sodefrin precursor-like factor (SPF), now indicates that evolutionary decoupling in this complex is pervasive. The evolutionary profiles of SPF and PRF are remarkably similar in that: (a) both genes exhibit high levels of sequence diversity both within and across taxa, (b) genetic diversity has been driven by strong positive selection, and (c) the genes have evolved heterogeneously in different salamander lineages. The composition of the pheromone signal as a whole, however, has experienced an extraordinary evolutionary transition. Whereas SPF has been retained throughout the 100 MY radiation of salamanders, PRF has only recently been recruited to a pheromone function (27 million years ago). When SPF and PRF coexist in the same clade, they show contrasting patterns of evolution. When one shows rapid evolution driven by positive selection, the other shows neutral divergence restrained by purifying selection. In one clade, the origin and subsequent rapid evolution of PRF appear to have interfered with the evolution and persistence of SPF, leading to a pattern of evolutionary replacement. Overall, these two pheromone genes provide a revealing window on the dynamics that drive the evolution of multiple traits in a signaling complex.     

Pushing, pulling and trapping--modes of motor protein supported protein translocation

Protein translocation across the cellular membranes is an ubiquitous and crucial activity of cells. This process is mediated by translocases that consist of a protein conducting channel and an associated motor protein. Motor proteins interact with protein substrates and utilize the free energy of ATP binding and hydrolysis for protein unfolding, translocation and unbinding. Since motor proteins are found either at the cis- or trans-side of the membrane, different mechanisms for translocation have been proposed. In the Power stroke model, cis-acting motors are thought to push, while trans-motors pull on the substrate protein during translocation. In the Brownian ratchet model, translocation occurs by diffusion of the unfolded polypeptide through the translocation pore while directionality is achieved by trapping and refolding. Recent insights in the structure and function of the molecular motors suggest that different mechanisms can be employed simultaneously.