植物转基因沉默研究进展

随着转基因技术在植物中的广泛应用,转基因沉默受到越来越多的重视。转基因沉默可发生在转录和转录后两种水平,其基本特征就是依赖于同源的重复序列。转基因的重复拷贝间,转基因与同源的内源基因间及RNA病毒与同源转基因间都会发生基因沉默。可能有不同的机制导致转基因沉默,本文综述了转基因沉默的机理研究及转基因沉默在植物抗病基因工程和植物功能基因组学方面的应用 。     

Long noncoding RNA LINC01234 promoted cell proliferation and invasion via miR-1284/TRAF6 axis in colorectal cancer

Colorectal cancer is one of the most common and leading malignancies globally. Long noncoding RNAs (lncRNAs) function as potentially critical regulator in colorectal cancer. LINC01234, a novel lncRNA in tumor biology, regulates the progression of various tumors. However, the tumorigenic mechanism of LINC01234 in colorectal cancer is still unclear. This study was performed with the aim to prospectively investigate clinical significance, effect, and mechanism of lncRNA LINC01234 in colorectal cancer. First, we found that LINC01234, localized in the cytoplasm, was increased in both colorectal cancer cell lines and tissues. Subsequent functional assays suggested LINC01234 knockdown suppressed cell proliferation, migration, and invasion of colorectal cancer cells, while blocked cell cycle and induced cell apoptosis. Moreover, we identified that miR-1284 was target of LINC01234, we further demonstrated a negative correlation with LINC01234 in colorectal cancer tissues and cells. Furthermore, miR-1284 targeted and suppressed tumor necrosis factor receptor–associated factor 6 (TRAF6). Loss-of-function assay revealed that LINC01234 silencing suppressed colorectal cancer progression through inhibition of miR-1284. In vivo subcutaneous xenotransplanted tumor model indicated LINC01234 knockdown inhibited in vivo tumorigenic ability of colorectal cancer via downregulation of TRAF6. Collectively, this study clarified the biological significance of LINC01234/miR-1284/TRAF6 axis in colorectal cancer progression, providing insights into LINC01234 as novel potential therapeutic target for colorectal cancer therapeutic from bench to clinic.     

Chlorimuron ethyl as a new selectable marker for disrupting genes in the insect-pathogenic fungus Metarhizium robertsii

A lack of selectable markers was a hindrance in investigating gene function in Metarhizium robertsii. A reliable Agrobacterium-mediated transformation system based on the use of chlorimuron ethyl as the selectable marker was developed which could serve as a useful tool to inactivate genes involved in insect pathogenicity.     

In vitro eradication of abasic site-mediated DNA–peptide/protein cross-links by Escherichia coli long-patch base excision repair

Apurinic/apyrimidinic (AP or abasic) sites are among the most abundant DNA lesions. Numerous proteins within different organisms ranging from bacteria to human have been demonstrated to react with AP sites to form covalent Schiff base DNA–protein cross-links (DPCs). These DPCs are unstable due to their spontaneous hydrolysis, but the half-lives of these cross-links can be as long as several hours. Such long-lived DPCs are extremely toxic due to their large sizes, which physically block DNA replication. Therefore, these adducts must be promptly eradicated to maintain genome integrity. Herein, we used in vitro reconstitution experiments with chemically synthesized, stable, and site-specific Schiff base AP-peptide/protein cross-link analogs to demonstrate for the first time that this type of DPC can be repaired by Escherichia coli (E. coli) long-patch base excision repair. We demonstrated that the repair process requires a minimum of three enzymes and five consecutive steps, including: (1) 5′-DNA strand incision of the DPC by endonuclease IV; (2 to 4) strand-displacement DNA synthesis, removal of the 5′-deoxyribose phosphate-peptide/protein adduct-containing flap, and gap-filling DNA synthesis by DNA polymerase I; and (5) strand ligation by a ligase. We further demonstrated that endonuclease IV plays a major role in incising an AP-peptide cross-link within E. coli cell extracts. We also report that eradicating model AP-protein (11.2–36.1 kDa) DPCs is less efficient than that of an AP-peptide_10mer cross-link, supporting the emerging model that proteolysis is likely required for efficient DPC repair.     

Effects of a moderate-intensity static magnetic field and adriamycin on K562 cells

The aim of this study was to investigate whether a moderate‐intensity static magnetic field (SMF) can enhance the killing effect of adriamycin (ADM) on K562 cells, and to explore the effects of SMF combined with ADM on K562 cells. We analyzed the metabolic activity of cells, cell cycle distribution, DNA damage, change in cell ultrastructure, and P‐glycoprotein (P‐gp) expression after K562 cells were exposed continuously to a uniform 8.8 mT SMF for 12 h, with or without ADM. Our results showed that the SMF combined with ADM (25 ng/ml) significantly inhibited the metabolic activity of K562 cells (P < 0.05), while neither ADM nor the SMF alone affected the metabolic activity of these cells. Cell ultrastructure was altered in the SMF + ADM group. For example, cell membrane was depressed, some protuberances were observable, and vacuoles in the cytoplasm became larger. Cells were arrested at the G2/M phase and DNA damage increased after cells were treated with the SMF plus ADM. ADM also induced the P‐gp expression. In contrast, in the SMF group and SMF + ADM group, the P‐gp expression was decreased compared with the ADM group. Taken together, our results showed that the 8.8 mT SMF enhanced the cytotoxity potency of ADM on K562 cells, and the decrease in P‐gp expression may be one reason underlying this effect. Bioelectromagnetics 32:191–199, 2011. © 2010 Wiley‐Liss, Inc.