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The maternally expressed zebrafish T-box gene eomesodermin regulates organizer formation 总被引:5,自引:0,他引:5
Bruce AE Howley C Zhou Y Vickers SL Silver LM King ML Ho RK 《Development (Cambridge, England)》2003,130(22):5503-5517
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Involvement of ERK in BMP-2 induced osteoblastic differentiation of mesenchymal progenitor cell line C3H10T1/2 总被引:10,自引:0,他引:10
The signaling mechanisms responsible for bone morphogenetic protein (BMP) induced osteoblast differentiation remains poorly understood. Previous research demonstrated that Smad proteins are the substrates and the mediators of BMP bound serine/threonine receptor kinase. In the present study, we examined the possible involvement of extracellular signal-regulated kinase (Erk) in the BMP induced osteoblast differentiation of mesenchymal progenitor cell C3H10T1/2. Our results indicate that BMP-2 inducement increased MAP kinase activity in mesenchymal progenitor cell line C3H10T1/2. Contrary to previous reports, this increased MAP kinase activity showed a latent but sustained pattern. Elevation of Erk1 and Erk2 protein levels was observed simultaneously. RT-PCR results demonstrated that the elevation of Erk protein level in BMP-2 induced cells was from the upregulation of mRNA expression. Furthermore, upregulated Erk proteins present enhanced phosphorylation. By using a dominant-negative Erk2 cell line, we demonstrated that nonfunctional Erk2 partially eliminated BMP-2 induced cell proliferation and ALP activity in the C3H10T1/2 cell. These results indicate that Erk is involved in BMP-2 induced osteoblast differentiation. The results also demonstrate that a latent and sustained signaling pattern exists in BMP induced signaling cascade. 相似文献
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Hepatitis delta virus (HDV) is a satellite virus of the hepatitis B virus (HBV) which provides the surface antigen for the viral coat. The RNA genome of HDV encodes two proteins, the small delta antigen and the large delta antigen, which differ only with the latter having an additional 19 amino acids at the C-terminus. Previously, we have shown that dAg24-50, a synthetic peptide corresponding to residues 24-50 of the N-terminal leucine-repeat region of hepatitis delta antigen, binds to the viral RNA and forms an alpha-helical conformation in TFE-containing solution. However, it exhibited low alpha-helicity (less than 5%) in the absence of TFE. In order to obtain biologically active delta antigen peptides with higher structural stability in solution, an N-capping 21-residue polypeptide corresponding to residues 24-38 of hepatitis delta antigen (dAg(Cap24-38am)) was synthesized and, surprisingly, its solution structure was found to be a stable alpha-helix (64%) by circular dichroism and 1H NMR techniques. Moreover, the structure of the capping box shows the characteristic L-shaped bend perpendicular to the helix axis. This structural knowledge provides a molecular basis for understanding the role of the N-terminal leucine-repeat region of hepatitis delta antigen and has a significant potential for the development of diagnostic and therapeutic methods for HDV. 相似文献
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Lack of obvious 50 kilobase pair DNA fragments in DNA fragmentation factor 45-deficient thymocytes upon activation of apoptosis 总被引:1,自引:0,他引:1
Zhang J Lee H Lou DW Bovin GP Xu M 《Biochemical and biophysical research communications》2000,274(1):225-229
The DNA fragmentation factor 45 (DFF45/ICAD) is a key subunit of a heterodimeric DNase complex critical for the induction of DNA fragmentation during apoptosis in vivo. To further assess the importance of DFF45 in chromosomal DNA degradation, we induced apoptosis in wild-type control and DFF45 deficient thymocytes and compared the cleavage of chromosomal DNA to 50 kilobase pair size fragments. We found that there is a lack of obvious large chromosomal DNA fragments upon treatments by various apoptotic agents in DFF45 deficient thymocytes. The major organ systems in the DFF45 mutant mice either two months or fifteen months of age appear normal. These results suggest that functional DFF45 is required for cleavage of DNA into both large size and oligonucleosomal size fragments in thymocytes during apoptosis. However, deficiency in DFF45 apparently does not significantly affect normal mouse development and tissue homeostasis. 相似文献
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应用脱氧核糖降解法研究了离体条件下Cu,Zn-SOD与H2O2反应产生·OH,并对其机理进行了探讨。H2O2可使Cu,Zn-SOD失活,在失活过程中有·OH产生,甲酸钠和苯甲酸钠均能不同程度地保护Cu,Zn-SOD和降低H2O2与Cu,Zn-SOD反应中·OH的产额;热失活SOD也可和H2O2反应生成·OH,且效能高于活性Cu,Zn-SOD;用螫合剂脱去Cu,Zn-SOD的金属辅基后,脱辅基的SOD蛋白不能和H2O2反应产生·OH;Cu2+和H2O2反应产生·OH的效率很高,而Zn2+产生·OH的效率很低。实验结果提示Cu,Zn-SOD与H2O2反应产生的·OH可能是SOD活性中心的Cu2+与H2O2发生Fenton反应的结果. 相似文献