How baculovirus polyhedra fit square pegs into round holes to robustly package viruses

Natural protein crystals (polyhedra) armour certain viruses, allowing them to survive for years under hostile conditions. We have determined the structure of polyhedra of the baculovirus Autographa californica multiple nucleopolyhedrovirus (AcMNPV), revealing a highly symmetrical covalently cross‐braced robust lattice, the subunits of which possess a flexible adaptor enabling this supra‐molecular assembly to specifically entrap massive baculoviruses. Inter‐subunit chemical switches modulate the controlled release of virus particles in the unusual high pH environment of the target insect's gut. Surprisingly, the polyhedrin subunits are more similar to picornavirus coat proteins than to the polyhedrin of cytoplasmic polyhedrosis virus (CPV). It is, therefore, remarkable that both AcMNPV and CPV polyhedra possess identical crystal lattices and crystal symmetry. This crystalline arrangement must be particularly well suited to the functional requirements of the polyhedra and has been either preserved or re‐selected during evolution. The use of flexible adaptors to generate a powerful system for packaging irregular particles is characteristic of the AcMNPV polyhedrin and may provide a vehicle to sequester a wide range of objects such as biological nano‐particles.     

Correlation analysis between three novel SNPs of the Src gene in bovine and milk production traits

As an essential signaling modulator, Src gene appears to be necessary for increased expression of the prolactin receptor, normal downstream signaling, and alveolar cell organization. In this study, we detected the polymorphism of Src gene by polymerase chain reaction-restriction fragment length polymorphism assay (PCR-RFLP) and DNA sequencing methods in 985 individuals from three Chinese cattle breeds. Three novel single nucleotide polymorphisms (SNPs) (g.14062C>T ss161151834, g.17302G>A ss161151835, g.18107T>C ss161151836) were detected. Least squares analysis showed that cows with g.14062C>T-CC genotypes and g.18107T>C-TT genotypes had the highest protein rate, while the cows with g.17302G>A-GG genotype had higher 305 d milk yield (p < 0.05), fat yield (p < 0.01) and protein yield (p < 0.01) than the ones with genotypes g.17302G>A-GA. These results revealed the statistical significant effects of three SNPs of the Src gene on the milk production traits in Chinese Holstein. In addition, based on the nine genotypes constructed from 27 combined haplotypes, the association analysis between combined haplotypes and milk production traits was carried out. Statistic results showed that the cows with combined haplotypes H2H4(CCGATT) had the highest fat rate and the highest protein rate and the cows with combined haplotypes H1H8(TCGATC) and H3H7(TCGGCC) had greater 305 d mild yield than H1H2(CCAATC)(P < 0.05). Our finding demonstrated that the Src gene possibly contributed to conducting association analysis and can be recognized as genetic marker in milk production traits and other performance for animal breeding and genetics.     

Differential expression of a novel gene <Emphasis Type="Italic">BRE</Emphasis> (TNFRSF1A modulator/BRCC45) in response to stress and biological signals

Stress-responsive genes play critical roles in many biological functions that includes apoptosis, survival, differentiation and regeneration. We have identified a novel stress-responsive gene called BRE which interacts with TNF-receptor-1 and blocks the apoptotic effect of TNF-α. BRE enhances tumor growth in vivo and is up-regulated in hepatocellular and esophageal carcinomas. BRE also regulates the ubiquitination of the DNA repair complex BRCC, and the synthesis of steroid hormones. Here, we examined BRE-mRNA in cells after treatments with UV and ionizing radiation (IR). UV and IR treatment alone suppressed BRE-mRNA levels by more than 90% at 24 h, while hydroxyurea, fluorodeoxyuridine, aphidicolin, known inhibitors of S-phase DNA synthesis, had no significant effect. BRE protein expression was unaltered in cells treated with TNF-α, Interleukin-1 and Dexamethasone, while a threefold increase was observed following chorionic gonadotropin exposure. Although BRE plays a regulatory role in many different pathways, yet its expression is apparently under very stringent control.     

Subunit–subunit interactions are weakened in mutant forms of acetohydroxy acid synthase insensitive to valine inhibition

In acetohydroxy acid synthase from Streptomyces cinnamonensis mutants affected in valine regulation, the impact of mutations on interactions between the catalytic and the regulatory subunits was examined using yeast two-hybrid system. Mutations in the catalytic and the regulatory subunits were projected into homology models of the respective proteins. Two changes in the catalytic subunit, E139A (α domain) and ΔQ217 (β domain), both located on the surface of the catalytic subunit dimer, lowered the interaction with the regulatory subunit. Three consecutive changes in the N-terminal part of the regulatory subunit were examined. Changes G16D and V17D in a loop and adjacent α-helix of ACT domain affected the interaction considerably, indicating that this region might be in contact with the catalytic subunit during allosteric regulation. In contrast, the adjacent mutation L18F did not influence the interaction at all. Thus, L18 might participate in valine binding or conformational change transfer within the regulatory subunits. Shortening of the regulatory subunit to 107 residues reduced the interaction essentially, suggesting that the C-terminal part of the regulatory subunit is also important for the catalytic subunit binding.     

Analysis of mitochondrial DNA mutations in D-loop region in thyroid lesions

Background

Mitochondrial defects have been associated with various human conditions including cancers.

Methods

We analyzed the mutations at the mitochondrial DNA (mtDNA) in patients with different thyroid lesions. In particular, in order to investigate if the accumulation of mtDNA mutations play a role in tumor progression, we studied the highly variable main control region of mtDNA, the displacement-loop (D-loop) in patients with non-tumor nodular goiters, with benign thyroid adenomas, and with malignant thyroid carcinomas. Total thyroid tumor or goiter samples were obtained from 101 patients, matched with nearby normal tissue and blood from the same subject.

Results

Noticeably, mitochondrial microsatellite instability (mtMSI) was detected in 2 of 19 nodular goiters (10.53%), and 8 of 77 (10.39%) malignant thyroid carcinomas. In addition, 6 patients, including 5 (6.49%) with malignant thyroid carcinomas and 1 (5.26%) with nodular goiter, were found to harbor point mutations. The majority of the mutations detected were heteroplasmic.

General significance

Our results indicate that mtDNA alterations in the D-loop region could happen before tumorigenesis in thyroid, and they might also accumulate during tumorigenesis.     

Shielding effect of monovalent and divalent cations on solid-phase DNA hybridization: surface plasmon resonance biosensor study

Solid-phase hybridization, i.e. the process of recognition between DNA probes immobilized on a solid surface and complementary targets in a solution is a central process in DNA microarray and biosensor technologies. In this work, we investigate the simultaneous effect of monovalent and divalent cations on the hybridization of fully complementary or partly mismatched DNA targets to DNA probes immobilized on the surface of a surface plasmon resonance sensor. Our results demonstrate that the hybridization process is substantially influenced by the cation shielding effect and that this effect differs substantially for solid-phase hybridization, due to the high surface density of negatively charged probes, and hybridization in a solution. In our study divalent magnesium is found to be much more efficient in duplex stabilization than monovalent sodium (15 mM Mg²⁺ in buffer led to significantly higher hybridization than even 1 M Na⁺). This trend is opposite to that established for oligonucleotides in a solution. It is also shown that solid-phase duplex destabilization substantially increases with the length of the involved oligonucleotides. Moreover, it is demonstrated that the use of a buffer with the appropriate cation composition can improve the discrimination of complementary and point mismatched DNA targets.     

Multilocus sequence typing and virulence factors analysis of Escherichia coli O157 strains in China

Escherichia coli O157:H7, an important food-borne pathogen, has become a major public health concern worldwide. The aim of this study was to investigate the molecular epidemiologic feature of E. coli O157:H7 strains in China. 105 E. coli O157:H7 isolates were collected from various hosts and places over 9 years. A multilocus sequence typing scheme (MLST) was applied for bacteria genotyping and polymerase chain reaction (PCR) was used for virulence factor identification. Seven new MLST sequence types (STs), namely ST836, ST837, ST838, ST839, ST840, ST841, and ST842 were identified, which grouped into two lineages. Phylogenetic analysis suggested that the most two frequent STs in China, ST837 and ST836, may be the derivatives of E. coli O157:H7 Sakai or E. coli O157:H7 EDL933. Geographical diversity and host variety of E. coli O157:H7 were observed in China. In addition, the different distribution of tccp was detected. The data presented herein provide new insights into the molecular epidemiologic feature of E. coli O157:H7, and aid in the investigation of the transmission regularity and evolutionary mechanism of E. coli O157:H7.     

Involvement of c‐Jun N‐terminal kinase and extracellular signal‐regulated kinase 1/2 in EGF‐induced angiogenesis

Angiogenesis is a process during which endothelial cells divide and migrate to form new capillaries from the preexisting blood vessels. The present study was designed to investigate whether MAPKs (mitogen‐activated protein kinases) play crucial roles in regulating EGF (epidermal growth factor)‐induced endothelial cell angiogenesis. Our results showed that EGF stimulated HUVEC (human umbilical vein endothelial cells) proliferation in a concentration‐dependent manner, of which the maximum effective concentration of EGF was 10 ng/ml. Western blot analysis showed that EGF at 10 ng/ml significantly induced the phosphorylation of ERK1/2 (extracellular signal‐regulated kinase 1 and 2) and p38 kinase at 5 min, while it induced the phosphorylation of JNK/SAPK (c‐Jun N‐terminal kinase/stress‐activated protein kinase) at 15 min. Further results showed that a JNK/SAPK inhibitor, SP600125, and a specific siRNA JNK/SAPK could both significantly inhibit EGF‐induced tube formation in HUVEC cells, and an ERK1/2 inhibitor PD098059 could also block the tube formation in some content, while a p38 inhibitor SB203580 failed to do so. Furthermore, only SP600125 significantly inhibited EGF‐induced HUVEC cell proliferation under no cytotoxic concentration, so did JNK/SAPK siRNA. In conclusion, JNK/SAPK and ERK1/2 signals therefore play critical roles in EGF‐mediated HUVEC cell angiogenesis.