siRNA-mediated downregulation of TC21 sensitizes esophageal cancer cells to cisplatin

AIM： To determine the functional significance of TC21 in esophageal squamous cell carcinoma （ESCC）. METHODS： TC21 siRNA transfection was carried out using Hyperfectamine to knock down TC21, and tran- scripts were analyzed by reverse transcription-poly- merase chain reaction and protein by Western blotting.We demonstrated the effect of TC21 downregulation of cell signaling in esophageal cancer cells by assess- ing the phosphorylation status of its downstream tar- gets, phosphoinositide 3-kinase （PI3K）, phosphatase and tensin homolog （PTEN）, protein kinase B （pAl〈t）, nuclear factor-KB （NF-~B） and cyclinD1 using specific antibodies. Cell survival analysis after cisplatin treat- ment was carried out by cell viability assay and cell cycle analysis using flow cytometry. RESULTS： TC21 knockdown in human ESCC cell line TEl3 cells, showed only a marginal increase （14.2%） in cell death compared with control cells. The expres- sions of the signaling proteins PI3K and pAkt, transcrip- tion factor NF-KB, and cell cycle protein cyclin D1 were markedly decreased in response to TC21 downregula- tion, whereas the level of pPTEN, an antagonist of PI3K, was increased. In addition, we evaluated the potential of TC21 as a putative target for sensitizing ESCC cells to the chemotherapeutic agent cisplatin. Increased cell death （38.4%） was observed in cells treated with cis- platin after TC21 knockdown compared with cells which were treated with cisplatin alone （20% cell death）. CONCLUSION： Results suggest that TC21 mediates its effects via the PI3K-Akt pathway, NF-KB and cyclin D1, and enhances chemoresistance in esophageal cancer cells.

转录后基因沉默与植物的病毒抗性

转录后基因沉默 (PTGS)是近 10年发现的一种生物 (特别是真核生物 )细胞抵抗外来核酸入侵及保持生物自身基因组完整性的防御机制 ,特别是与生物的病毒抗性密切相关。PTGS最初在植物内发现 ,近几年又分别在真菌、动物等生物细胞内发现。经过 10年的研究 ,我们对PTGS的机制和特点有了相当的了解。这不但对深入地了解基因的表达调控机制意义重大 ,而且还可为人们如何调控和利用PTGS奠定了基础。本文从PTGS的特点、PTGS与病毒抗性、PTGS在真核生物内发生的广泛性等方面进行综述 。

Role of ADAM10 and ADAM17 in CD16b Shedding Mediated by Different Stimulators

Objective To investigate the main proteinases responsible for CD16b shedding under different stimulators. Methods HEK293 cell line stably expressing CD16b was constructed by lentivirus system. The cell line was then overexpressed with a disintegrin and metalloproteinase 10 （ADAM10） or ADAM17, sup- pressed with short hairpin RNA of ADAM10 or ADAM I 7, and reconstituted with ADAM 10 or ADAM17, respectively. After each treatment, the cell line was stimulated with ionomycin or phorbol 12-myristate- 13-acetate （PMA） for 12 hours. The soluble CD 16b released from cell membrane was detected by immuno- precipition and immunoblot. Quantitation was then implemented to compare the amount of soluble CD 16b in cell supernatant after stimulation. Results HEK293 cell line stably expressing CD16b was successfully established. When CDI6b ex- pressing cell line was overexpressed with ADAM 10, shedding of CD 16b was increased after stimulation with ionomycin but not PMA; when the cell line overexpressed with ADAM I7, shedding of CDI6b was increased after stimulation with PMA but not ionomycin. Similarly, when ADAM10 was suppressed by short hairpin RNA, CD 16b shedding was decreased after stimulation with ionomycin; when ADAM 17 was suppressed by short hairpin RNA, CD16b shedding was decreased after stimulation with PMA. The shedding of CD16b was increased again when CD16b expressing cell line was reconstituted with ADAM10 and stimulated by ionomycin or reconstituted with ADAM 17 and stimulated by PMA. Conclusions Both ADAM10 and ADAM17 could shed CD16b, but they possess differed prefer- ences. ADAM10 is the main sheddase under stimulation of ionomycin, while ADAM17 is the main sheddase under stimulation of PMA.

The effect of AD-VEGF-siRNA on the expression of vascular endothelial growth factor in osteosarcoma-bearing nude mice

Objective： To explore the influence of AD-VEGF-siRNA on the expression of vascular endothelial growth factor （VEGF） in neoplasm and blood serum. Methods： Transplantable model of human osteosarcoma was successfully established by the way of subcutaneous injection of VEGF highly expressed human MG63 osteosarcoma cells. These mice were divided randomly into three groups： AD-VEGF-siRNA group, 15 mice; AD-EGFP group, 15 mice; PBS group, 15 mice. Three mice were additionally raised without any treatment. The drug was injected intratumorally 200 μL at each time, once a day. The total dose of virus was 2 × 10^9 pfu. Three osteosarcema-bearing mice of each group were sacrificed at 11th, 14th ,17th day after the implantation of MG63 cells. The expression of VEGF in implanted tumors and blood serum was detected by ELISA methods. Then the left mice were all sacrificed at the end of experiment （19th day）. The expression of VEGF in implanted tumors was detected by RT-PCR and immune histochemistry methods, and that in implanted tumors and blood serum was detected by ELISA methods. Results： （1） Tumors in mice could be seen at 5th day from the implantation of MG63 cells. （2） The expression of VEGF could be detected in all groups by RT-PCR and immune histochemistry, Which was much lower in the group receiving AD-VEGF-siRNA therapy than two control groups （P 〈 0.05）. （3） The expression of VEGF in blood serum of osteosarcoma-bearing mice was much higher than that of three healthy mice by ELISA （P 〈 0.05）. （4） The expression of VEGF in blood serum and neoplasm in AD-VEGF-siRNA group was much lower than that in two control groups （P 〈 0.05）. Conclusion： AD-VEGF-siRNA could effectively inhibited VEGF expression in vivo. This technology would bring some good references for our therapy of antiangiogenesis in osteosarcoma.

microRNAs in a multicellular green alga Volvox carteri

microRNAs(miRNAs)have emerged as key components in the eukaryotic gene regulatory network.We and others have previously identified many miRNAs in a unicellular green alga,Chlamydomonas reinhardtii.To investigate whether miRNA-mediated gene regulation is a general mechanism in green algae and how miRNAs have been evolved in the green algal lineage,we examined small RNAs in Volvox carteri,a multicellular species in the same family with Chlamydomonas reinhardtii.We identified 174 miRNAs in Volvox,with many of them being highly enriched in gonidia or somatic cells.The targets of the miRNAs were predicted and many of them were subjected to miRNA-mediated cleavage in vivo,suggesting that miRNAs play regulatory roles in the biology of green algae.Our catalog of miRNAs and their targets provides a resource for further studies on the evolution,biological functions,and genomic properties of miRNAs in green algae.

Transient silencing mediated by in vitro synthesized double-stranded RNA indicates that PsCdc14 is required for sporangial development in a soybean root rot pathogen

In many eukaryotic organisms, Cdcl4 phosphatase regulates multiple biological events during anaphase and is essential for mitosis. It has been shown that Cdcl4 is required for sporulation in the potato blight pathogen Phytophthora infestans; howev- er, the role that the Cdcl4 homolog （PsCdcl4） plays in the soil-borne soybean root rot pathogen P. sojae remains ambiguous. PsCdc14 is highly expressed in spornlation, zoospore, and cyst life stages, but not in vegetative mycelia and infection stages, suggesting that it contributes to asexual reproduction and thus the spread of the disease. Double-stranded RNA （dsRNA） medi- ates gene silencing, a post-transcriptional and highly conserved process in eukaryotes, involving specific gene silencing through degradation of target mRNA. We combined in vitro dsRNA synthesis and a polyethylene glycol-mediated transfor- marion system to construct a dsRNA-mediated transient gene silencing system; and then performed a functional analysis of PsCdcl4 in P. sojae. PsCdc14 mRNA was dramatically reduced in transformants after protoplasts were exposed in in vitro synthesized PsCdc14 dsRNA, resulting in low sporangial production and abnormal development in P. sojae silencing lines. Furthermore, dsRNA-mediated transient gene silencing could enable elucidation of P. sojae rapid gene function, facilitating our understanding of the development and pathogenicity mechanisms of this oomycete fungus.

ADAR-mediated RNA editing in non-coding RNA sequences

Adenosine to inosine （A-to-I） RNA editing is the most abundant editing event in animals. It converts adenosine to inosine in double-stranded RNA regions through the action of the adenosine deaminase acting on RNA （ADAR） proteins. Editing of pre-mRNA coding regions can alter the protein codon and increase functional diversity. However, most of the A-to-I editing sites occur in the non-coding regions of pre-mRNA or mRNA and non-coding RNAs. Untranslated regions （UTRs） and introns are located in pre-rnRNA non-coding regions, thus A-to-I editing can influence gene expression by nuclear retention, degrada- tion, alternative splicing, and translation regulation. Non-coding RNAs such as microRNA （miRNA）, small interfering RNA （siRNA） and long non-coding RNA （lncRNA） are related to pre-mRNA splicing, translation, and gene regulation. A-to-I edit- ing could therefore affect the stability, biogenesis, and target recognition of non-coding RNAs. Finally, it may influence the function of non-coding RNAs, resulting in regulation of gene expression. This review focuses on the function of ADAR-mediated RNA editing on mRNA non-coding regions （UTRs and introns） and non-coding RNAs （miRNA, siRNA, and IncRNA）.

Non-coding RNAs mediate the rearrangements of genomic DNA in ciliates

Most eukaryotes employ a variety of mechanisms to defend the integrity of their genome by recognizing and silencing parasitic mobile nucleic acids.However,recent studies have shown that genomic DNA undergoes extensive rearrangements,including DNA elimination,fragmentation,and unscrambling,during the sexual reproduction of ciliated protozoa.Non-coding RNAs have been identified to program and regulate genome rearrangement events.In Paramecium and Tetrahymena,scan RNAs(scnRNAs)are produced from micronuclei and transported to vegetative macronuclei,in which scnRNA elicits the elimination of cognate genomic DNA.In contrast,Piwi-interacting RNAs(piRNAs)in Oxytricha enable the retention of genomic DNA that exhibits sequence complementarity in macronuclei.An RNA interference(RNAi)-like mechanism has been found to direct these genomic rearrangements.Furthermore,in Oxytricha,maternal RNA templates can guide the unscrambling process of genomic DNA.The non-coding RNA-directed genome rearrangements may have profound evolutionary implications,for example,eliciting the multigenerational inheritance of acquired adaptive traits.