An atypical mitogen-activated protein kinase controls cytokinesis and flagellar motility during male gamete formation in a malaria parasite

The transmission of malaria parasites to the mosquito depends critically on the rapid initiation of sexual reproduction in response to triggers from the mosquito midgut environment. We here identify an essential function for an atypical mitogen-activated protein kinase of the rodent malaria parasite Plasmodium berghei, Pbmap-2, in male sexual differentiation and parasite transmission to the mosquito. A deletion mutant no longer expressing the Pbmap-2 protein develops as wild type throughout the asexual erythrocytic phase of the life cycle. Gametocytes, the sexual transmission stages, form normally and respond in vitro to the appropriate environmental cues by rounding up and emerging from their host cells. However, microgametocytes fail to release flagellated microgametes. Female development is not affected, as judged by the ability of macrogametes to become cross-fertilized by microgametes from a donor strain. Cellular differentiation of Pbmap-2 KO microgametocytes is blocked at a late stage of male gamete formation, after replication and mitoses have been completed and axonemes have been assembled. These data demonstrate a function for Pbmap-2 in initiating cytokinesis and axoneme motility, possibly downstream of a cell cycle checkpoint for the completion of replication and/or mitosis, which are extraordinarily rapid in the male gametocyte.     

Induction of apoptosis by a novel indirubin-5-nitro-3'-monoxime, a CDK inhibitor, in human lung cancer cells

A novel indirubin analog, indirubin-5-nitro-3'-monoxime, inhibited cell proliferation against various human cancer cells. Additional studies indicate that the mechanism of action of this analog against human lung cancer cells might be to arrest cell cycle progression at the G2/M phase and induce apoptosis via p53- and mitochondria-dependent pathways. These data suggest that indirubin-5-nitro-3'-monoxime might be a novel candidate for development of anticancer agents.     

Improvement of a microbial fuel cell performance as a BOD sensor using respiratory inhibitors

Studies were made to improve the performance of a microbial fuel cell (MFC) as a biochemical oxygen demand (BOD) sensor. The signal from MFCs decreased in the presence of electron acceptors of higher redox potential such as nitrate and oxygen. The addition of azide and cyanide did not change the signal in the absence of the electron acceptors. The respiratory inhibitors eliminated the inhibitory effects of the electron acceptors on the current generation from MFCs. Similar results were obtained using oligotrophic MFCs fed with an environmental sample that contained nitrate. The use of the respiratory inhibitors is therefore recommended for the accurate BOD measurement of environmental samples containing nitrate and/or oxygen with an MFC-type BOD sensor.     

Kaposi's sarcoma-associated herpesvirus/human herpesvirus 8 RTA reactivates murine gammaherpesvirus 68 from latency

Murine gammaherpesvirus 68 (MHV-68), Kaposi's sarcoma-associated herpesvirus (HHV-8), and Epstein-Barr virus (EBV) are all members of the gammaherpesvirus family, characterized by their ability to establish latency in lymphocytes. The RTA protein, conserved in all gammaherpesviruses, is known to play a critical role in reactivation from latency. Here we report that HHV-8 RTA, not EBV RTA, was able to induce MHV-68 lytic viral proteins and DNA replication and processing and produce viable MHV-68 virions from latently infected cells at levels similar to those for MHV-68 RTA. HHV-8 RTA was also able to activate two MHV-68 lytic promoters, whereas EBV RTA was not. In order to define the domains of RTA responsible for their functional differences in viral promoter activation and initiation of the MHV-68 lytic cycle, chimeric RTA proteins were constructed by exchanging the N-terminal and C-terminal domains of the RTA proteins. Our data suggest that the species specificity of MHV-68 RTA resides in the N-terminal DNA binding domain.     

Oxidative stress-dependent structural and functional switching of a human 2-Cys peroxiredoxin isotype II that enhances HeLa cell resistance to H2O2-induced cell death

Although biochemical properties of 2-Cys peroxiredoxins (Prxs) have been extensively studied, their real physiological functions in higher eukaryotic cells remain obscure and certainly warrant further study. Here we demonstrated that human (h) PrxII, a cytosolic isotype of human 2-Cys Prx, has dual functions as a peroxidase and a molecular chaperone, and that these different functions are closely associated with its adoption of distinct protein structures. Upon exposure to oxidative stress, hPrxII assumes a high molecular weight complex structure that has a highly efficient chaperone function. However, the subsequent removal of stressors induces the dissociation of this protein structure into low molecular weight proteins and triggers a chaperone-to-peroxidase functional switch. The formation of a high molecular weight hPrxII complex depends on the hyperoxidation of its N-terminal peroxidatic Cys residue as well as on its C-terminal domain, which contains a "YF motif" that is exclusively found in eukaryotic 2-Cys Prxs. A C-terminally truncated hPrxII exists as low and oligomeric protein species and does not respond to oxidative stress. Moreover, this C-terminal deletion of hPrxII converted it from an oxidation-sensitive to a hyperoxidation-resistant form of peroxidase. When functioning as a chaperone, hPrxII protects HeLa cells from H(2)O(2)-induced cell death, as measured by a terminal deoxynucleotidyltransferase-mediated dUTP nick-end labeling assay and fluorescence-activated cell sorting analysis.     

Stereoselective synthesis of novel thioiso dideoxy nucleosides with exocyclic methylene as potential antiviral agents

Novel thioiso pyrimidine and purine nucleosides substituted with exocyclic methylene have been synthesized, starting from D-xylose. Cyclization of the dimesylate to the 4-thiosugar 6a proceeded in pure SN2 reaction in the presence of allylic functional group.     

Stereoselective synthesis of 3-hydroxymethyl-D-cyclopentenone, the versatile intermediate for the synthesis of carbocyclic nucleosides

The preparative and stereoselective synthesis (45- 50% overall yields, >50 g scale) of the key carbasugars 7a-d was achieved from D-ribose via stereoselective Grignard reaction and oxidative rearrangement as key reactions.