Microheliella maris (Microhelida ord. n.), an ultrastructurally highly distinctive new axopodial protist species and genus, and the unity of phylum Heliozoa

A new heliozoan, Microheliella maris, has sufficiently distinctive ultrastructure to merit a new order, Microhelida. Its 18S and 28S rRNA genes were sequenced earlier under the informal name 'marine microheliozoan'; we here sequenced its Hsp90 gene. A three-gene tree suggests that it is distantly related to centrohelids and others in chromist subkingdom Hacrobia; but it is too divergent to be placed accurately by few genes. Unlike centrohelids, its central spherical centrosome has two concentric granular shells and a dense core devoid of a trilaminar central disc. Microtubules radiate from the centrosomal shells. Unlike centrohelids, axopodia have only three microtubules, fixed basally by dense plasma membrane anchors, and bear terminal and lateral haptosome-like extrusomes. As in the heliomonad Heliomorpha, the centrosome is embedded in a nuclear cavity, and centrosomal microtubules traverse the nucleus inside cytoplasmic channels. A novel filogranular network interconnects mitochondria, ER, and plasma membrane. The microbody is attached to the nucleus and mitochondrion, which has vermicular tubular cristae. We group Microhelida and Heliomonadida, purged of dissimilar flagellates, as a new tubulicristate class Endohelea within phylum Heliozoa. Previously misassigned GenBank 18S rDNA sequences reveal Microhelida as diverse and ancient. We discuss principles underlying the biogenesis and diversity of axopodial patterns.     

Loss of CCDC6 affects cell cycle through impaired intra-S-phase checkpoint control

In most cancers harboring Ccdc6 gene rearrangements, like papillary thyroid tumors or myeloproliferative disorders, the product of the normal allele is supposed to be functionally impaired or absent. To address the consequence of the loss of CCDC6 expression, we applied lentiviral shRNA in several cell lines. Loss of CCDC6 resulted in increased cell death with clear shortening of the S phase transition of the cell cycle. Upon exposure to etoposide, the cells lacking CCDC6 did not achieve S-phase accumulation. In the absence of CCDC6 and in the presence of genotoxic stress, like etoposide treatment or UV irradiation, increased accumulation of DNA damage was observed, as indicated by a significant increase of pH2Ax Ser139. 14-3-3σ, a major cell cycle regulator, was down-regulated in CCDC6 lacking cells, regardless of genotoxic stress. Interestingly, in the absence of CCDC6, the well-known genotoxic stress-induced cytoplasmic sequestration of the S-phase checkpoint CDC25C phosphatase did not occur. These observations suggest that CCDC6 plays a key role in cell cycle control, maintenance of genomic stability and cell survival and provide a rational of how disruption of CCDC6 normal function contributes to malignancy.     

Cleavage mediated by the P15 domain of bacterial RNase P RNA

Independently folded domains in RNAs frequently adopt identical tertiary structures regardless of whether they are in isolation or are part of larger RNA molecules. This is exemplified by the P15 domain in the RNA subunit (RPR) of the universally conserved endoribonuclease P, which is involved in the processing of tRNA precursors. One of its domains, encompassing the P15 loop, binds to the 3'-end of tRNA precursors resulting in the formation of the RCCA-RNase P RNA interaction (interacting residues underlined) in the bacterial RPR-substrate complex. The function of this interaction was hypothesized to anchor the substrate, expose the cleavage site and result in re-coordination of Mg(2+) at the cleavage site. Here we show that small model-RNA molecules (~30 nt) carrying the P15-loop mediated cleavage at the canonical RNase P cleavage site with significantly reduced rates compared to cleavage with full-size RPR. These data provide further experimental evidence for our model that the P15 domain contributes to both substrate binding and catalysis. Our data raises intriguing evolutionary possibilities for 'RNA-mediated' cleavage of RNA.     

Role of intermonomer ionic bridges in the stabilization of the actin filament

Filament formation is required for most of the functions of actin. However, the intermonomer interactions that stabilize F-actin have not been elucidated because of a lack of an F-actin crystal structure. The Holmes muscle actin model suggests that an ionic interaction between Arg-39 of one monomer and Glu-167 of an adjacent monomer in the same strand contributes to this stabilization. Yeast actin has an Ala-167 instead. F-actin molecular dynamics modeling predicts another interaction between Arg-39 of one monomer and Asp-275 of an opposing strand monomer. In Toxoplasma gondii actin, which forms short stubby filaments, the Asp-275 equivalent is replaced by Arg leading to a potential filament-destabilizing charge-charge repulsion. Using yeast actin, we tested the effect of A167E as a potential stabilizer and A167R and D275R as potential filament disruptors. All mutations caused abnormal growth and mitochondrial malfunction. A167E and D275R actins polymerize normally and form relatively normal appearing filaments. A167R nucleates filaments more slowly and forms filament bundles. The R39D/A167R double mutant, which re-establishes an ionic bond in the opposite orientation, reverses this polymerization and bundling defect. Stoichiometric amounts of yeast cofilin have little effect on wild-type and A167E filaments. However, D275R and A167R actin depolymerization is profound with cofilin. Although our results suggest that disruption of an interaction between Arg-39 and Asp-275 is not sufficient to cause fragmentation, it suggests that it changes filament stability thereby disposing it for enhanced cofilin depolymerizing effects. Ala-167 results demonstrate the in vivo and in vitro importance of another potential Arg-39 ionic interaction.     

Photoprotective effects of glucomannan isolated from Candida utilis

Glucomannans belong to yeast and fungal cell wall polysaccharides with known immunostimulatory and radioprotective effects. However, glucomannan protective effects against pathological consequences of skin exposure to short wavelength solar light, ultraviolet (UV) radiation, are unclear. Herein, a highly branched glucomannan (GM) isolated from the cell wall of Candida utilis, a member of the alpha-(1-->6)-D-mannan group, was tested for its photoprotective effects in an in vitro model of UVB-irradiated human keratinocytes and an in vivo model of UV-induced erythema formation in human volunteers. GM suppressed the UVB-induced decrease of keratinocyte viability, which was connected with the suppression of UVB-induced keratinocyte apoptosis. GM reduced UVB-mediated caspase activation together with suppression of DNA fragment release into the cytoplasm. Furthermore, GM suppressed UVB-induced gene expression of pro-inflammatory markers including nuclear factor kappa B, inducible nitric oxide synthase, interleukins 8 and 1, together with suppression of prostaglandin E2 and interleukin 1alpha protein release. In vivo, GM decreased UV-induced skin erythema formation, which was correlated with a decrease of phosholipase A(2) activity within the stratum corneum. It could be concluded that GM isolated from C. utilis possesses significant photoprotective effects on human keratinocytes in vitro as well as in vivo.     

Occurrence of Hepatitis C Virus infection in type 2 diabetic patients attending Plateau state specialist hospital Jos Nigeria

Background

Hepatitis E virus (HEV) is highly endemic in several African countries with high mortality rate among pregnant women. The prevalence of antibodies to HEV in Ghana is not known. Therefore we evaluated the prevalence of anti-HEV IgG and anti-HEV IgM among pregnant women seen between the months of January and May, 2008 at the Obstetrics and Gynaecology Department, Korle-Bu Teaching Hospital, Accra, Ghana.

Results

One hundred and fifty-seven women provided blood samples for unlinked anonymous testing for the presence of antibodies to HEV. The median age of participants was 28.89 ± 5.76 years (range 13–42 years). Of the 157 women tested, HEV seroprevelance was 28.66% (45/157). Among the seropositive women, 64.40% (29/45) tested positive for anti-HEV IgM while 35.60% (16/45) tested positive to HEV IgG antibodies. HEV seroprevalence was highest (46.15%) among women 21–25 years of age, followed by 42.82% in = 20 year group, then 36.84% in = 36 year group. Of the 157 women, 75.79% and 22.92% were in their third and second trimesters of pregnancy, respectively. Anti-HEV antibodies detected in women in their third trimester of pregnancy (30.25%) was significantly higher, P < 0.05, than in women in their second trimester of pregnancy (25.0%).

Conclusion

Consistent with similar studies worldwide, the results of our studies revealed a high prevalence of HEV infection in pregnant women.