Signal sequence- and translation-independent mRNA localization to the endoplasmic reticulum

The process of mRNA localization typically utilizes cis-targeting elements and trans-recognition factors to direct the compartmental organization of translationally suppressed mRNAs. mRNA localization to the endoplasmic reticulum (ER), in contrast, occurs via a co-translational, signal sequence/signal recognition particle (SRP)-dependent mechanism. We have utilized cell fractionation/cDNA microarray analysis, shRNA-mediated suppression of SRP expression, and mRNA reporter construct studies to define the role of the SRP pathway in ER-directed mRNA localization. Cell fractionation studies of mRNA partitioning between the cytosol and ER demonstrated the expected enrichment of cytosolic/nucleoplasmic protein-encoding mRNAs and secretory/integral membrane protein-encoding mRNAs in the cytosol and ER fractions, respectively, and identified a subpopulation of cytosolic/nucleoplasmic protein-encoding mRNAs in the membrane-bound mRNA pool. The latter finding suggests a signal sequence-independent pathway of ER-directed mRNA localization. Extending from these findings, mRNA partitioning was examined in stable SRP54 shRNA knockdown HeLa cell lines. shRNA-directed reductions in SRP did not globally alter mRNA partitioning patterns, although defects in membrane protein processing were observed, further suggesting the existence of multiple pathways for mRNA localization to the ER. ER localization of GRP94-encoding mRNA was observed when translation was disabled by mutation of the start codon/insertion of a 5'UTR stem-loop structure or upon deletion of the encoded signal sequence. Combined, these data indicate that the mRNA localization to the ER can be conferred independent of the signal sequence/SRP pathway and suggest that mRNA localization to the ER may utilize cis-encoded targeting information.     

The Component and Functional Pathways of Gut Microbiota are Altered in Populations with Poor Sleep Quality – A Preliminary Report

With the development of genome sequencing, many researchers have investigated the mechanism by which the intestinal microbiota influences sleep across the brain-gut axis. However, the relationship between gut microbiota and sleep disorder remains unclear. Thus, we studied the difference in gut microbiota composition between poor sleep quality- and normal populations, which helps set the ground for future research. The recruited college students provided baseline information and stool samples and completed the Pittsburgh Sleep Quality Index (PSQI). We compared the two groups’ gut microbiota composition and functional differentiation by using the 16S rRNA gene sequencing analysis. The main bacterial difference and the most critical effect were mainly concentrated within Tenericutes and Elusimicrobia. Compared with the healthy control group, some functions of the gut microbiota were impaired in the poor sleep quality group, such as butanoate metabolism and propanoate metabolism. Bacterial taxa with significant differences raised the possibility for future diagnosis and treatment of sleep problems.     

circ-ZNF609: A potent circRNA in human cancers

Circular RNAs (circRNAs) are a novel group of endogenous RNAs with a circular structure. Growing evidence indicates that circRNAs are involved in a variety of human diseases including malignancies. CircRNA ZNF609 (circ-ZNF609), derived from the ZNF609 gene sequence, has been demonstrated to be involved in the development and progression of many diseases. circ-ZNF609 is thought to be a viable diagnostic and prognostic biomarker for several diseases and might be a new therapeutic target, but further research is needed to accelerate clinical application. Here, we review the biogenesis and function of circRNAs and the functional roles and molecular mechanism related to circ-ZNF609 in neoplasms and other diseases.     

The Fungal Exopolysaccharide Galactosaminogalactan Mediates Virulence by Enhancing Resistance to Neutrophil Extracellular Traps

Of the over 250 Aspergillus species, Aspergillus fumigatus accounts for up to 80% of invasive human infections. A. fumigatus produces galactosaminogalactan (GAG), an exopolysaccharide composed of galactose and N-acetyl-galactosamine (GalNAc) that mediates adherence and is required for full virulence. Less pathogenic Aspergillus species were found to produce GAG with a lower GalNAc content than A. fumigatus and expressed minimal amounts of cell wall-bound GAG. Increasing the GalNAc content of GAG of the minimally pathogenic A. nidulans, either through overexpression of the A. nidulans epimerase UgeB or by heterologous expression of the A. fumigatus epimerase Uge3 increased the amount of cell wall bound GAG, augmented adherence in vitro and enhanced virulence in corticosteroid-treated mice to levels similar to A. fumigatus. The enhanced virulence of the overexpression strain of A. nidulans was associated with increased resistance to NADPH oxidase-dependent neutrophil extracellular traps (NETs) in vitro, and was not observed in neutropenic mice or mice deficient in NADPH-oxidase that are unable to form NETs. Collectively, these data suggest that cell wall-bound GAG enhances virulence through mediating resistance to NETs.     

Partitioning and translation of mRNAs encoding soluble proteins on membrane-bound ribosomes

In eukaryotic cells, it is generally accepted that protein synthesis is compartmentalized; soluble proteins are synthesized on free ribosomes, whereas secretory and membrane proteins are synthesized on endoplasmic reticulum (ER)-bound ribosomes. The partitioning of mRNAs that accompanies such compartmentalization arises early in protein synthesis, when ribosomes engaged in the translation of mRNAs encoding signal-sequence-bearing proteins are targeted to the ER. In this report, we use multiple cell fractionation protocols, in combination with cDNA microarray, nuclease protection, and Northern blot analyses, to assess the distribution of mRNAs between free and ER-bound ribosomes. We find a broad representation of mRNAs encoding soluble proteins in the ER fraction, with a subset of such mRNAs displaying substantial ER partitioning. In addition, we present evidence that membrane-bound ribosomes engage in the translation of mRNAs encoding soluble proteins. Single-cell in situ hybridization analysis of the subcellular distribution of mRNAs encoding ER-localized and soluble proteins identify two overall patterns of mRNA distribution in the cell-endoplasmic reticular and cytosolic. However, both partitioning patterns include a distinct perinuclear component. These results identify previously unappreciated roles for membrane-bound ribosomes in the subcellular compartmentalization of protein synthesis and indicate possible functions for the perinuclear membrane domain in mRNA sorting in the cell.     

Serum SP-D is a marker of lung injury in rats

Pulmonary surfactant protein D (SP-D) is expressed in alveolar type II and bronchiolar epithelial cells and is secreted into alveoli and conducting airways. However, SP-D has also been measured in serum and is increased in patients with acute respiratory distress syndrome, pulmonary fibrosis, and alveolar proteinosis. To demonstrate that SP-D can be measured in rat serum, we instilled rats with keratinocyte growth factor, which produces type II cell hyperplasia and an increase in SP-D in bronchoalveolar lavage fluid (BALF). To evaluate serum SP-D as a biomarker of lung injury, we examined several injury models. In rats treated with 1 unit of bleomycin, serum SP-D was elevated on days 3, 7, 14, and 28 after instillation, and SP-D mRNA was increased in focal areas as detected by in situ hybridization. However, there was no increase in whole lung SP-D mRNA when the expression was normalized to whole lung 18S rRNA. After instillation of 2 units of bleomycin, the serum levels of SP-D were higher, and SP-D was also increased in BALF and lung homogenates. In another model of subacute injury, serum SP-D was increased in rats treated with paraquat plus oxygen. Finally to evaluate acute lung injury, we instilled rats with HCl; SP-D was increased at 4 h after instillation. Our data indicate that serum SP-D may be a useful indicator of lung injury and type II cell hyperplasia in rats.     

Effect of Yeast Cell Morphology,Cell Wall Physical Structure and Chemical Composition on Patulin Adsorption

The capability of yeast to adsorb patulin in fruit juice can aid in substantially reducing the patulin toxic effect on human health. This study aimed to investigate the capability of yeast cell morphology and cell wall internal structure and composition to adsorb patulin. To compare different yeast cell morphologies, cell wall internal structure and composition, scanning electron microscope, transmission electron microscope and ion chromatography were used. The results indicated that patulin adsorption capability of yeast was influenced by cell surface areas, volume, and cell wall thickness, as well as 1,3-β-glucan content. Among these factors, cell wall thickness and 1,3-β-glucan content serve significant functions. The investigation revealed that patulin adsorption capability was mainly affected by the three-dimensional network structure of the cell wall composed of 1,3-β-glucan. Finally, patulin adsorption in commercial kiwi fruit juice was investigated, and the results indicated that yeast cells could adsorb patulin from commercial kiwi fruit juice efficiently. This study can potentially simulate in vitro cell walls to enhance patulin adsorption capability and successfully apply to fruit juice industry.     

2型单纯疱疹病毒体外感染周期的研究进展

2型单纯疱疹病毒(Herpes simplex virus type 2,HSV-2)是引起生殖器疱疹的主要病原体。生殖器疱疹主要表现为生殖器和肛周皮肤黏膜疱疹或溃疡,是一种慢性、复发性、难以治愈的性传播疾病,临床治疗多以抑制病毒复制的核苷类药物阿昔洛韦及其衍生物更昔洛韦、喷昔洛韦等为主。这些药物对缓解症状、缩短病程有一定作用,但难以达到根治的目的,长期应用易产生耐药,且对其合并症基本无效。作用于HSV-2其他感染周期的药物成为人类探索的新领域。HSV-2感染宿主细胞是一个复杂的多阶段过程,包括黏附、穿入、核转运、基因组复制、衣壳组装、子代病毒释放等多个步骤,涉及多种细胞和病毒蛋白的活性。本文对HSV-2体外感染周期详细步骤及其分子机制作一综述,以期深入了解其感染机制,并为研制作用于不同感染阶段的抗HSV-2药物提供参考。     

共球藻纲丝状藻中国新记录属种——洪泛拟寇丽藻

从甘肃省张掖市黑河流域分离了一株不分枝的丝状绿藻,对其进行纯培养并保藏于中国科学院淡水藻种库,编号FACHB 2451。形态观察表明,该藻株具有相对较长的营养细胞 (细胞长为宽的3~8倍)、双叶形的片状叶绿体、末端细胞顶端钝圆或略尖细等特征。结合形态比较和基于18S rDNA 基因序列的系统发育分析,确定该藻株为中国淡水共球藻纲新记录属种——洪泛拟寇丽藻 (Koliellopsis inundata Lokhorst)。分子系统发育研究结果表明,所分离的藻株与分离自比利时与荷兰边境农地的洪泛拟寇丽藻模式藻株序列相似度极高,且拟寇丽藻属与寇丽藻属、针丝藻属和拟针丝藻属等不分枝丝状拟寇丽藻科成员亲缘关系密切,可以较好地聚成一个亚支。