Relationships of the Insect-Pathogenic Order Entomophthorales (Zygomycota, Fungi) Based on Phylogenetic Analyses of Nuclear Small Subunit Ribosomal DNA Sequences (SSU rDNA)

We sequenced the nuclear small subunit of ribosomal DNA (SSU rDNA) from seven species within the insect-pathogenic order Entomophthorales. These sequences were aligned with other published SSU rDNA sequences and phylogenies were inferred using phenetic and cladistic methods. Based on three different phylogenetic methods the Entomophthorales (excludingBasidiobolus ranarum) is monophyletic;B. ranarumwas more closely related to chytrids from Chytridiales and Neocallimasticales than to Entomophthorales, as was proposed by Nagahamaet al.(Mycologia87:203–209, 1995). Nuclear characters (large nuclei containing conspicuous condensed chromatin and lack of a prominent nucleolus) were of predictive value for the monophyly of the family Entomophthoraceae. Conidial characters separate the Entomophthoraceae, which only includes obligate pathogens, into at least two lineages: one lineage with uninucleate conidia and another with multinucleate conidia. The two species ofConidiobolusstudied were paraphyletic in our analyses and only distantly related to each other. This information may prove to be important in the use of these fungi as biocontrol agents.     

Dodecameric structure and ATPase activity of the human TIP48/TIP49 complex

TIP48 and TIP49 are two related and highly conserved eukaryotic AAA(+) proteins with an essential biological function and a critical role in major pathways that are closely linked to cancer. They are found together as components of several highly conserved chromatin-modifying complexes. Both proteins show sequence homology to bacterial RuvB but the nature and mechanism of their biochemical role remain unknown. Recombinant human TIP48 and TIP49 were assembled into a stable high molecular mass equimolar complex and tested for activity in vitro. TIP48/TIP49 complex formation resulted in synergistic increase in ATPase activity but ATP hydrolysis was not stimulated in the presence of single-stranded, double-stranded or four-way junction DNA and no DNA helicase or branch migration activity could be detected. Complexes with catalytic defects in either TIP48 or TIP49 had no ATPase activity showing that both proteins within the TIP48/TIP49 complex are required for ATP hydrolysis. The structure of the TIP48/TIP49 complex was examined by negative stain electron microscopy. Three-dimensional reconstruction at 20 A resolution revealed that the TIP48/TIP49 complex consisted of two stacked hexameric rings with C6 symmetry. The top and bottom rings showed substantial structural differences. Interestingly, TIP48 formed oligomers in the presence of adenine nucleotides, whilst TIP49 did not. The results point to biochemical differences between TIP48 and TIP49, which may explain the structural differences between the two hexameric rings and could be significant for specialised functions that the proteins perform individually.     

Dietary Resistant Starch Reduces Histone Acetylation on the Glucose-Dependent Insulinotropic Polypeptide Gene in the Jejunum

We have reported that dietary resistant starch (RS) reduces glucose-dependent insulinotropic polypeptide (GIP) mRNA levels along the jejunoileum in both normal and diabetic rats. In this study, we found that jejunal reduction of the GIP gene by feeding normal rats dietary RS was associated with decreases in histone H3 and H4 acetylation on the promoter/enhancer region of the gene.     

Regulation of cytokinesis by membrane trafficking involving small GTPases and the ESCRT machinery

During cell division, cells undergo membrane remodeling to achieve changes in their size and shape. In addition, cell division entails local delivery and retrieval of membranes and specific proteins as well as remodeling of cytoskeletons, in particular, upon cytokinetic abscission. Accumulating lines of evidence highlight that endocytic membrane removal from and subsequent membrane delivery to the plasma membrane are crucial for the changes in cell size and shape, and that trafficking of vesicles carrying specific proteins to the abscission site participate in local remodeling of membranes and cytoskeletons. Furthermore, the endosomal sorting complex required for transport (ESCRT) machinery has been shown to play crucial roles in cytokinetic abscission. Here, the author briefly overviews membrane-trafficking events early in cell division, and subsequently focus on regulation and functional significance of membrane trafficking involving Rab11 and Arf6 small GTPases in late cytokinesis phases and assembly of the ESCRT machinery in cytokinetic abscission.     

小肠干细胞的命运调控

小肠上皮具有快速更新的能力,是研究成体干细胞的理想系统.小肠上皮由绒毛和隐窝两部分组成,而位于小肠隐窝底部的小肠干细胞是其持续更新的源泉.近年来,以Lgr5为代表的小肠干细胞标记物的发现、Lgr5+小肠干细胞的分离培养和多种转基因小鼠模型的出现,极大地促进了对小肠干细胞自我更新和分化调控的研究,使得人们可以更加深入地认识小肠干细胞命运决定的分子机制.本文简要综述了近年来人们对Wnt,BMP,Notch和EGF等信号如何在小肠干细胞命运调控中发挥作用的认识.     

Current status of the organ replacement approach for malignancies and an overture for organ bioengineering and regenerative medicine

Significant achievements in the organ replacement approach for malignancies over the last 2 decades opened new horizons, and the age of “Transplant Oncology” has dawned. The indications of liver transplantation for malignancies have been carefully expanded by a strict patient selection to assure comparable outcomes with non-malignant diseases. Currently, the Milan criteria, gold standard for hepatocellular carcinoma, are being challenged by high-volume centers worldwide. Neoadjuvant chemoradiation therapy and liver transplantation for unresectable hilar cholangiocarcinoma has been successful in specialized institutions. For other primary and metastatic liver tumors, clinical evidence to establish standardized criteria is lacking. Intestinal and multivisceral transplantation is an option for low-grade neoplasms deemed unresectable by conventional surgery. However, the procedure itself is in the adolescent stage. Solid organ transplantation for malignancies inevitably suffers from “triple distress,” i.e., oncological, immunological, and technical. Organ bioengineering and regenerative medicine should serve as the “triple threat” therapy and revolutionize “Transplant Oncology.”     

Decorin has an appetite for endothelial cell autophagy

DCN (decorin), an extracellular matrix constituent and archetypical small leucine-rich proteoglycan (SLRP), acts as a soluble tumor repressor. DCN exerts high-affinity binding interactions with receptor tyrosine kinases and evokes receptor internalization consequent with lysosomal degradation for tumorigenic and angiogenic suppression. In our recent study, we discovered that DCN evokes synthesis of PEG3 (paternally expressed 3), an imprinted gene often silenced in various forms of cancer. Upon DCN stimulation, PEG3 relocalizes to BECN1- and LC3-positive phagophores. Importantly, PEG3 physically associates with BECN1- and LC3-containing supramolecular complexes, in a DCN-inducible manner, and PEG3 is necessary to maintain homeostatic levels of BECN1. Furthermore, DCN evokes a protracted autophagic program via transactivation of the BECN1 and MAPLC3A loci that is critically dependent on PEG3 expression. Mechanistically, DCN directly binds to the Ig domains 3–5 of the KDR/VEGFR2 ectodomain, in a region that partially overlaps with the canonical binding site for VEGFA. Therefore, we have unveiled a novel mechanism for a secreted proteoglycan to induce endothelial cell autophagy in a PEG3-dependent manner. These findings are consistent with earlier preclinical studies focusing on DCN-mediated tumorigenic and angiogenic suppression and may represent the mechanism of action to achieve these effects. Therefore, DCN and perhaps other members of this class of matrix constituents may represent a novel control of autophagy from the outside of the cells.