Dehydroascorbate reductase （DHAR） plays a critical role in the ascorbate-glutathione recycling reaction for most higher plants. To date, studies on DHAR in higher plants have focused largely on Arabidopsis and agric...Dehydroascorbate reductase （DHAR） plays a critical role in the ascorbate-glutathione recycling reaction for most higher plants. To date, studies on DHAR in higher plants have focused largely on Arabidopsis and agricultural plants, and there is virtually no information on the molecular characteristics of DHAR in gymnosperms. The present study reports the cloning and characteristics of a DHAR （PbDHAR） from a pine, Pinus bungeana Zucc. ex Endl. The PbDHAR gene encodes a protein of 215 amino acid residues with a calculated molecular mass of 24.26 kDa. The predicted 3-D structure of PbDHAR showed a typical glutathione S-transferase fold. Reverse transcripUon-polymerase chain reaction revealed that the PbDHAR was a constitutive expression gene in P. bungeana. The expression level of PbDHAR mRNA in P. bungeana seedlings did not show significant change under high temperature stress. The recombinant PbDHAR was overexpressed in Escherichia coil following purification with affinity chromatography. The recombinant PbDHAR exhibited enzymatic activity （19.84 i.mnol/min per mg） and high affinity （a Krn of 0.08 mM） towards the substrates dehydroascorbate （DHA）. Moreover, the recombinant PbDHAR was a thermostable enzyme, and retained 77% of its initial activity at 55℃. The present study is the first to provide a detailed molecular characterization of the DHAR in P. bungeana.展开更多
Oncogenic microRNAs are essential components in regulating the gene expression of cancer cells. Especially miR21, which is a major player involved of tumor initiation, progression, invasion and metastasis in several c...Oncogenic microRNAs are essential components in regulating the gene expression of cancer cells. Especially miR21, which is a major player involved of tumor initiation, progression, invasion and metastasis in several cancers. The delivery of anti-miR21 sequences has significant potential for cancer treatment. Nevertheless, since anti-miR21 sequences are extremely unstable and they need to obtain certain concentration to function, it is intensely difficult to build an effective delivery system for them.The purpose of this work is to construct a self-assembled glutathione(GSH)-responsive system with tumor accumulation capacity for effective anti-miR21 delivery and cancer therapy. A novel drug delivery nanosphere carrying millions of anti-miR21 sequences was developed through the rolling circle transcription(RCT) method. GSH-responsive cationic polymer polyethyleneimine(pOEI) was synthesized to protect the nanosphere from degradation by Dicer or other RNase in normal cells and optimize the pompon-like nanoparticle to suitable size. Dehydroascorbic acid(DHA), a targeting molecule, which is a substrate of glucose transporter 1(GLUT 1) and highly expressed on malignant tumor cells, was connected to pOEI through PEG, and then the polymer was used for contracting a RNA nanospheres into nanopompons. The anti-miR21 nanopompons showed its potential for effective cancer therapy.展开更多
基金Supported by the National Natural Science Foundation of China (30800873)the State Key Basic Research and Development Plan of China(2009CB119104)
文摘Dehydroascorbate reductase （DHAR） plays a critical role in the ascorbate-glutathione recycling reaction for most higher plants. To date, studies on DHAR in higher plants have focused largely on Arabidopsis and agricultural plants, and there is virtually no information on the molecular characteristics of DHAR in gymnosperms. The present study reports the cloning and characteristics of a DHAR （PbDHAR） from a pine, Pinus bungeana Zucc. ex Endl. The PbDHAR gene encodes a protein of 215 amino acid residues with a calculated molecular mass of 24.26 kDa. The predicted 3-D structure of PbDHAR showed a typical glutathione S-transferase fold. Reverse transcripUon-polymerase chain reaction revealed that the PbDHAR was a constitutive expression gene in P. bungeana. The expression level of PbDHAR mRNA in P. bungeana seedlings did not show significant change under high temperature stress. The recombinant PbDHAR was overexpressed in Escherichia coil following purification with affinity chromatography. The recombinant PbDHAR exhibited enzymatic activity （19.84 i.mnol/min per mg） and high affinity （a Krn of 0.08 mM） towards the substrates dehydroascorbate （DHA）. Moreover, the recombinant PbDHAR was a thermostable enzyme, and retained 77% of its initial activity at 55℃. The present study is the first to provide a detailed molecular characterization of the DHAR in P. bungeana.
基金supported by the grants from National Science Fund for Distinguished Young Scholars(81425023,China)Program of Shanghai Academic Research Leader(18XD1400500,China)
文摘Oncogenic microRNAs are essential components in regulating the gene expression of cancer cells. Especially miR21, which is a major player involved of tumor initiation, progression, invasion and metastasis in several cancers. The delivery of anti-miR21 sequences has significant potential for cancer treatment. Nevertheless, since anti-miR21 sequences are extremely unstable and they need to obtain certain concentration to function, it is intensely difficult to build an effective delivery system for them.The purpose of this work is to construct a self-assembled glutathione(GSH)-responsive system with tumor accumulation capacity for effective anti-miR21 delivery and cancer therapy. A novel drug delivery nanosphere carrying millions of anti-miR21 sequences was developed through the rolling circle transcription(RCT) method. GSH-responsive cationic polymer polyethyleneimine(pOEI) was synthesized to protect the nanosphere from degradation by Dicer or other RNase in normal cells and optimize the pompon-like nanoparticle to suitable size. Dehydroascorbic acid(DHA), a targeting molecule, which is a substrate of glucose transporter 1(GLUT 1) and highly expressed on malignant tumor cells, was connected to pOEI through PEG, and then the polymer was used for contracting a RNA nanospheres into nanopompons. The anti-miR21 nanopompons showed its potential for effective cancer therapy.
