Characterization of protein arginine methyltransferase of TgPRMT5 in Toxoplasma gondii.

BACKGROUND: Protein arginine methylation is a prevalent post-translational modification. The protein arginine methyltransferase family (PRMT) is involved in many cellular processes in eukaryotes, including transcriptional regulation, epigenetic regulation, RNA metabolism, and DNA damage repair. Toxoplasma gondii, an opportunistic protozoan parasite, encodes five conserved PRMTs. PRMT5 is thought to be responsible for substantial PRMT activity in T. gondii; however, it has not yet been characterized. METHODS: We tagged the 3' end of the endogenous TgPRMT5 genomic locus with sequence encoding a 3X hemagglutinin (HA) epitope. IFA and WB were performed to check the expression and subcellular localization of TgPRMT5 in tachyzoites and bradyzoites. In vitro methylation assays were performed to determine whether endogenous TgPRMT5 has arginine methyltransferase activity. RESULTS: IFA and WB results showed that T. gondii PRMT5 (TgPRMT5) was localized in the cytoplasm in the tachyzoite stage; however, it shifts largely to the nuclear compartment in the bradyzoite stage. The in vitro methylation showed that TgPRMT5 has authentic type II PRMT activity and forms monomethylarginines and symmetric dimethylarginines. CONCLUSIONS: We determined the expression and cellular localization of TgPRMT5 in tachyzoites and bradyzoites and confirmed its type II PRMT activity. We demonstrated the major changes in expression and cellular localization of TgPRMT5 during the tachyzoite and bradyzoite stages in T. gondii. Our findings suggest that TgPRMT5 protein may be involved in tachyzoite-bradyzoite transformation.

[Preliminary application of a mosquito densovirus-mediated artificial intron in vitro and in vive of mosquito].

An artificial intron consisting of the 5'-donor site (from the first intron of the human beta-globin gene) and the 3'-acceptor site (from the intron of an immunoglobulin gene heavy chain variable region) was obtained with a splice overlap extension PCR and was then inserted in frame into the coding sequence of nostructural protein NS1 gene fused to GFP gene in a recombinant mosquito densovirus plasmid p7NS1-GFP. The constructed plasmid was named as p7NS1-Intron-GFP. The plasmid p7NS1-Intron-GFP was co transfected with the helper plasmid pUCA into C6/36 cells, then the packaged recombinant and wild type viruses were purified and recovered. The second-instars of Aedes albopictus larvae were exposed to recombinant and wild type virus mixed stock. The high level GFP expression in C6/36 cells and larvae was observed under fluorescence microscope, indicating that the inserted artificial intron exerted its normal function in self-splicing both in vitro and in vivo. This study laid a foundation for application of an artificial intron in insect cells and development of new strategy for genetic engineering technology of mosqtuito and its pathogens.

[Method of detection of soluble HLA-I and soluble HLA-I level alteration in storage blood].

Aim of this study was to develop the detection method of soluble human leukocyte antigens I (sHLA-I) and to explore sHLA-I level alteration in storage blood and its significance. sHLA-I level in sera of 60 Guangdong normal individuals and sHLA-I concentration in blood components from 20 donors quantitatively were detected by sandwich ELISA. The results showed that sensitivity of this assay was 2.84 ng/ml. Coefficients of variation were 5.80% within assays and 9.00% between assays respectively. The recovery rate was >/= 98.57%. The sHLA-I level of normal individuals in Guangdong was (699.54 +/- 360.10) ng/ml. sHLA-I in red blood cells stored for 28 days and in random-donor platelets were significantly higher than that in other blood components and their amount was proportionate to the number of residual donor leukocytes and to the length of storage. In conclusion, sandwich ELISA assay for detection of sHLA-I is a sensitive, specific and stable technique. Blood components with different concentration of sHLA-I may be chosen for clinical transfusion.