The motility of a human parasite, Toxoplasma gondii, is regulated by a novel lysine methyltransferase

Protozoa in the phylum Apicomplexa are a large group of obligate intracellular parasites. Toxoplasma gondii and other apicomplexan parasites, such as Plasmodium falciparum, cause diseases by reiterating their lytic cycle, comprising host cell invasion, parasite replication, and parasite egress. The successful completion of the lytic cycle requires that the parasite senses changes in its environment and switches between the non-motile (for intracellular replication) and motile (for invasion and egress) states appropriately. Although the signaling pathway that regulates the motile state switch is critical to the pathogenesis of the diseases caused by these parasites, it is not well understood. Here we report a previously unknown mechanism of regulating the motility activation in Toxoplasma, mediated by a protein lysine methyltransferase, AKMT (for Apical complex lysine (K) methyltransferase). AKMT depletion greatly inhibits activation of motility, compromises parasite invasion and egress, and thus severely impairs the lytic cycle. Interestingly, AKMT redistributes from the apical complex to the parasite body rapidly in the presence of egress-stimulating signals that increase [Ca²⁺] in the parasite cytoplasm, suggesting that AKMT regulation of parasite motility might be accomplished by the precise temporal control of its localization in response to environmental changes.     

PackHelix: a tool for helix-sheet packing during protein structure prediction

The three‐dimensional structure of a protein is organized around the packing of its secondary structure elements. Predicting the topology and constructing the geometry of structural motifs involving α‐helices and/or β‐strands are therefore key steps for accurate prediction of protein structure. While many efforts have focused on how to pack helices and on how to sample exhaustively the topologies and geometries of multiple strands forming a β‐sheet in a protein, there has been little progress on generating native‐like packings of helices on sheets. We describe a method that can generate the packing of multiple helices on a given β‐sheet for αβα sandwich type protein folds. This method mines the results of a statistical analysis of the conformations of αβ₂ motifs in protein structures to provide input values for the geometric attributes of the packing of a helix on a sheet. It then proceeds with a geometric builder that generates multiple arrangements of the helices on the sheet of interest by sampling through these values and performing consistency checks that guarantee proper loop geometry between the helices and the strands, minimal number of collisions between the helices, and proper formation of a hydrophobic core. The method is implemented as a module of ProteinShop. Our results show that it produces structures that are within 4–6 Å RMSD of the native one, regardless of the number of helices that need to be packed, though this number may increase if the protein has several helices between two consecutive strands in the sequence that pack on the sheet formed by these two strands. Proteins 2011; Published 2011 Wiley‐Liss, Inc.     

Identification, replication, and fine-mapping of Loci associated with adult height in individuals of african ancestry

Adult height is a classic polygenic trait of high heritability (h ² ∼0.8). More than 180 single nucleotide polymorphisms (SNPs), identified mostly in populations of European descent, are associated with height. These variants convey modest effects and explain ∼10% of the variance in height. Discovery efforts in other populations, while limited, have revealed loci for height not previously implicated in individuals of European ancestry. Here, we performed a meta-analysis of genome-wide association (GWA) results for adult height in 20,427 individuals of African ancestry with replication in up to 16,436 African Americans. We found two novel height loci (Xp22-rs12393627, P = 3.4×10⁻¹² and 2p14-rs4315565, P = 1.2×10⁻⁸). As a group, height associations discovered in European-ancestry samples replicate in individuals of African ancestry (P = 1.7×10⁻⁴ for overall replication). Fine-mapping of the European height loci in African-ancestry individuals showed an enrichment of SNPs that are associated with expression of nearby genes when compared to the index European height SNPs (P<0.01). Our results highlight the utility of genetic studies in non-European populations to understand the etiology of complex human diseases and traits.     

Maternal inheritance of plastids and mitochondria in Cycas L. (Cycadaceae)

Cycas is often considered a living fossil, thereby providing a unique model for revealing the evolution of spermatophytes. To date, the genetic inheritance of these archaic plants is not fully understood. The present study seeks to document the process of organelle inheritance in an interspecific cross of Cycas species. Extranuclear organelle DNA from chloroplasts and mitochondria was analyzed using both polymerase chain reaction-restriction fragment length polymorphism analysis and microscopy. Here, we show that the chloroplasts and mitochondria in the progeny of interspecific crosses between Cycas taitungensis and Cycas ferruginea were exclusively inherited from the female parent. Epifluorescence microscopic analyses of the pollen cells from Cycas elongata indicated that there was a significant degradation of organelle DNA in male reproductive cells following maturation; the DNA fluorescent signals were only seen after pollen mitosis two, but not detectable at mature stage. Lack of organelle DNA fluorescent signal in prothallial cells was confirmed by the absence of plastids and mitochondria in electronic microscopic images. In conclusion, these data suggest that the maternal plastid and mitochondrial inheritance in Cycas, native to the old world, are the same as seen in seed plants.     

miR-21 targets the tumor suppressor RhoB and regulates proliferation, invasion and apoptosis in colorectal cancer cells

It has become increasingly clear that microRNAs play an important role in many human diseases including cancer. Here, we show that expression of miR-21 in HEK293 and several colorectal cancer cells was found inversely correlated with ras homolog gene family, member B (RhoB) expression. miR-21 expression significantly suppressed RhoB 3' UTR luciferase-reporter activity, but the inhibitory effect was lost when the putative target sites were mutated. Exogenous miR-21 over-expression mimicked the effect of RhoB knockdown in promoting proliferation and invasion and inhibiting apoptosis, whereas anti-miR-21 or RhoB expression yielded opposite effects, in colorectal cancer cells. These results suggest that miR-21 is a regulator of RhoB expression and RhoB could be a useful target in exploring the potential therapeutic benefits of miR-21 mediated tumor cell behaviors in colorectal cancer.     

The increasing burden of imported chronic hepatitis B--United States, 1974-2008

Background

Without intervention, up to 25% of individuals chronically infected with hepatitis B virus (HBV) die of late complications, including cirrhosis and liver cancer. The United States, which in 1991 implemented a strategy to eliminate HBV transmission through universal immunization, is a country of low prevalence. Approximately 3,000–5,000 U.S.-acquired cases of chronic hepatitis B have occurred annually since 2001. Many more chronically infected persons migrate to the United States yearly from countries of higher prevalence. Although early identification of chronic HBV infection can reduce the likelihood of transmission and late complications, immigrants are not routinely screened for HBV infection during or after immigration.

Methods

To estimate the number of imported cases of chronic hepatitis B, we multiplied country-specific prevalence estimates by the yearly number of immigrants from each country during 1974–2008.

Results

During 1974–2008, 27.9 million immigrants entered the U.S. Sixty-three percent were born in countries of intermediate or high chronic hepatitis B prevalence (range 2%–31%). On average, an estimated 53,800 chronic hepatitis B cases were imported to the U.S. yearly from 2004 through 2008. The Philippines, China, and Vietnam contributed the most imported cases (13.4%, 12.5%, and 11.0%, respectively). Imported cases increased from an estimated low of 105,750 during the period 1974–1977 to a high of 268,800 in 2004–2008.

Conclusions

Imported chronic hepatitis B cases account for approximately 95% of new U.S. cases. Earlier case identification and management of infected immigrants would strengthen the U.S. strategy to eliminate HBV transmission, and could delay disease progression and prevent some deaths among new Americans.     

A Novel Targeted Multi-Functional Fusion Protein Possesses Inhibitory Activities Against Bacteria, Thrombin and Platelet Aggregation

In the present study, we designed a novel targeted multi-functional fusion protein LHAD composed of LL-37, FXa recognition peptide, hirudin-12-residue, AAP, and RGD peptide. It was expressed in the Pichia pastoris GS115 strain and purified by affinity chromatography. The in vitro studies suggested that the novel designed protein exhibited antibacterial activity, anti-platelet aggregation and anti-thrombin activities. Moreover, the capability of anti-thrombin was significantly increased compared to that of natural hirudin. Our study may provide a potential approach to design multi-functional drugs for the prevention and management of thrombosis.