The RNA helicase RHAU (DHX36) unwinds a G4-quadruplex in human telomerase RNA and promotes the formation of the P1 helix template boundary

Human telomerase RNA (hTR) contains several guanine tracts at its 5′-end that can form a G4-quadruplex structure. Previous evidence suggests that a G4-quadruplex within this region disrupts the formation of an important structure within hTR known as the P1 helix, a critical element in defining the template boundary for reverse transcription. RNA associated with AU-rich element (RHAU) is an RNA helicase that has specificity for DNA and RNA G4-quadruplexes. Two recent studies identify a specific interaction between hTR and RHAU. Herein, we confirm this interaction and identify the minimally interacting RNA fragments. We demonstrate the existence of multiple quadruplex structures within the 5′ region of hTR and find that these regions parallel the minimal sequences capable of RHAU interaction. We confirm the importance of the RHAU-specific motif in the interaction with hTR and demonstrate that the helicase activity of RHAU is sufficient to unwind the quadruplex and promote an interaction with 25 internal nucleotides to form a stable P1 helix. Furthermore, we have found that a 5′-terminal quadruplex persists following P1 helix formation that retains affinity for RHAU. Finally, we have investigated the functional implications of this interaction and demonstrated a reduction in average telomere length following RHAU knockdown by small interfering RNA (siRNA)

Role of seminal plasma in the anti-HIV-1 activity of candidate microbicides

BACKGROUND: Evaluation of microbicides for prevention of HIV-1 infection in macaque models for vaginal infection has indicated that the concentrations of active compounds needed for protection by far exceed levels sufficient for complete inhibition of infection in vitro. These experiments were done in the absence of seminal plasma (SP), a vehicle for sexual transmission of the virus. To gain insight into the possible effect of SP on the performance of selected microbicides, their anti-HIV-1 activity in the presence, and absence of SP, was determined. METHODS: The inhibitory activity of compounds against the X4 virus, HIV-1 IIIB, and the R5 virus, HIV-1 BaL was determined using TZM-bl indicator cells and quantitated by measuring β-galactosidase induced by infection. The virucidal properties of cellulose acetate 1,2-benzene-dicarboxylate (CAP), the only microbicide provided in water insoluble, micronized form, in the presence of SP was measured. RESULTS: The HIV-1 inhibitory activity of the polymeric microbicides, poly(naphthalene sulfonate), cellulose sulfate, carrageenan, CAP (in soluble form) and polystyrene sulfonate, respectively, was considerably (range ≈ 4 to ≈ 73-fold) diminished in the presence of SP (33.3%). Formulations of micronized CAP, providing an acidic buffering system even in the presence of an SP volume excess, effectively inactivated HIV-1 infectivity. CONCLUSION: The data presented here suggest that the in vivo efficacy of polymeric microbicides, acting as HIV-1 entry inhibitors, might become at least partly compromised by the inevitable presence of SP. These possible disadvantages could be overcome by combining the respective polymers with acidic pH buffering systems (built-in for formulations of micronized CAP) or with other anti-HIV-1 compounds, the activity of which is not affected by SP, e.g. reverse transcriptase and zinc finger inhibitors

Chlorinated Pyridazin-3-(2H)-ones as Novel Anti-Cancer Agents

Analogues of new lead structures, such as amido-2(5H)-furanones, bisarylated acrylic acids and 3(2H)-pyridazones, were prepared from mucochloric acid. Initially, these simple butenolides and analogues have been evaluated in tissue culture studies and subsequently, selected examples were tested in vivo on MAC 16 murine colon cancer cell lines. Bis-arylated methacrylic acids showed in addition to a moderate cytotoxicity an inhibition of tumor growth in vivo in mice. The xylene derivative MXAA displayed at 20mg/kg a 25% inhibition compared to 27% for the control (5-FU). The acetamido-furanone AAF displayed an IC50 of 18, 4 µM for the MAC 13 and MAC16 cell line, respectively and this translated into 26% inhibition of tumour growth in the transplanted MAC 16 cell line in mice. The unsubstituted pyridazine DCPYR, had a manifold higher in vitro activity, than the known arylated pyridazones and most interestingly this correlated well with the observed in vivo activity. Pyridazine DCPYR showed 53% inhibition of tumour growths in vivo in mice at a 50mg/kg dose and less weight loss was observed for this best agent compared to the anti-metabolite 5-FU, which served as standard. Abstrac

Cytokinesis: Closure resets your SIN

A new study of fission yeast cell division has revealed a coupling between cytoplasmic partitioning and the turning-off of cytokinesis signalling that may be mediated by asymmetric protein distribution