生物谷報道：目前臨床治療癌癥比較有效的方法主要是手術切除和放化療，其中放化療是大部分患者都要經歷的,，但是經過放化療的醫(yī)治依然還是會有殘留一些癌細胞,，近期來自普度大學的研究人員發(fā)現了一個也許在癌細胞抵御放化療再生作用中起到關鍵作用的機制
（蛋白），而且這一機制也許同樣在阿滋海默癥和心臟疾病中起作用,。這一研究成果發(fā)表在近日出版的EMBO J上,。
利用一種由普度大學發(fā)明的新型成像技術，華人科學家Chang-Deng Hu博士和其他研究人員發(fā)現之前認為存在于健康細胞核的一種蛋白實際上可以在細胞核和細胞質之間穿梭,，而且這種蛋白的穿梭作用是由細胞核中比鄰的另外一種蛋白調控的,。這兩種蛋白就是c-Jun和ATF2（AP-1蛋白復合物重要組成蛋白）。
AP-1：activating protein-1,，這種轉錄因子主要由Jun,、Fos、ATF及JDP亞家族組成, 亞家族單體以同源（homodimers）或異源二聚體（heterodimers）的形式結合DNA靶序列, 調節(jié)靶基因,，在細胞的正常生長和癌性轉化過程中起著重要作用,。AP-1的活性受多種核因子調節(jié)，同時單體間也存在相互促進或拮抗作用,。AP-1對各種刺激如應激、輻射或生長信號等作出生理或病理應答, 參與細胞的增殖,、分化和轉化等過程, 在腫瘤的形成,、轉移和侵襲中發(fā)揮重要作用, 已經有學者研究通過抑制AP-1活性來發(fā)展抗腫瘤藥物.
目前一般都認為健康細胞中的AP-1都是定位在細胞核中的，然而Chang-Deng Hu等研究人員通過F9小鼠畸形癌細胞系實驗發(fā)現ATF2蛋白有出核與入核結構信號（“nuclear export” and “uclear localization” signals）,，即能夠從細胞核到細胞質,，也能從細胞質回到細胞核。而且研究人員也發(fā)現當核內ATF2與c-Jun形成異源二聚體的時候,，穿膜信號就會被封閉,，ATF2就不能穿過核膜到細胞質中了。
臨床放化療手段主要是通過引發(fā)ATF2表達來治療癌癥,，但是根據實驗結果,，Chang-Deng Hu認為這樣過量表達出來的ATF2由細胞核內c-Jun不足，因此會大量積累到細胞質中,，而且除了觀察到小鼠腫瘤干細胞中有ATF2的積累,，研究人員還發(fā)現將這些細胞暴露在紫外光中會引起c-Jun蛋白的表達，與ATF2結合后導致穿梭過程的停止,，細胞死亡,。
之前的研究證明ATF2的過量表達會引起癌細胞對放化療的抵制，因此ATF2的穿梭機制也許在癌癥細胞抵御機理中起到重要的作用,，通過阻止ATF2從細胞核轉移到細胞質也許可以有效的增加癌癥治療的有效性,。
原始出處:
Liu, H., Deng, X., Shyu, Y., Li, J.J., Taparowsky, EJ., and Hu, C.-D. Mutual regulation of c-Jun and ATF2 by transcriptional activation and subcellular localization. The EMBO Journal, (2006) 25, 1058–1069
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延伸閱讀：有關ATF和c-JUN的關系
Daniel Panne, Tom Maniatis and Stephen C Harrison. Crystal structure of ATF-2/c-Jun and IRF-3 bound to the interferon- enhancer. The EMBO Journal (2004) 23, 4384–4393
簡介：
Chang-Deng Hu
主頁: http://people.pharmacy.purdue.edu/~cdhu/
1984年,，就讀于安徽 蚌埠醫(yī)學院（Bengbu Medical College）（美國認可的中國醫(yī)學院校之一）；
1987年,，獲得同濟醫(yī)科大學腫瘤免疫學碩士學位,；
1997年，獲得日本神戶大學（Kobe University）分子生物學博士學位,；
1997年-2000年,，日本神戶大學Assitant Professor；
2000年-2002年,，美國密歇根大學博士后,；
2002年-2003年，美國密歇根大學研究員,；
2003年-至今,，美國普度大學Assistant Professor of Medicinal Chemistry and Moleculary Pharmacology，
印第安納州Walther Cancer Institute研究員
Signal transduction, transcriptional regulation, drug discovery, C. elegans development, BiFC technology
Research
Protein-protein interactions are essential for transmitting extracellular signals into cells and for coordinating cellular functions. Although many interaction maps have been generated over the past few years using genome-wide approaches, such as yeast two-hybrid and proteomics, it remains a challenge to prove these interactions in vivo. We have developed a novel bimolecular fluorescence complementation (BiFC) assay to directly visualize protein-protein interactions in living cells (Molecular Cell, 9, 789-798, 2002). This assay is based on the formation of a bimolecular fluorescent complex between two halves of YFP (yellow fluorescent protein) fused to a pair of interaction partners. To study how each protein selects its interacting partners in response to specific signals, we have taken advantage of spectral variants of green fluorescent protein and further established a multicolor bimolecular fluorescence complementation (multicolor BiFC) assay (Nature Biotechnology, 21, 539-545, 2003). The multicolor BiFC assay allows us to study multiple protein interactions simultaneously in the same cell. Recently, the identification of several fluorescent protein fragments derived from the new fluorescent proteins, Venus, Citrine and Cerulean, has further expanded our capability to analyze protein-protein interactions under physiological conditions (BioTechniques, 40, 61-66, 2006).
AP-1 in cancer: Activator protein 1 (AP-1) belongs to the basic region leucine zipper (bZIP) family of transcription factors and functions as homodimers or heterodimers formed among the members of Fos, Jun, ATF2 and Maf family of proteins to regulate gene expression. AP-1 activity can be induced by both physiological stimuli and environmental stresses, thereby regulating a wide range of cellular processes including cell proliferation, differentiation, death, and stress responses. Deregulated AP-1 activity is implicated in many human diseases including cancer. Furthermore, AP-1 proteins also interact with many other transcriptional regulatory proteins, such as the Rel family, SMADs family, hormone receptors, and coactivators CBP/p300. These cross-family interactions further increase the complexity of the regulation of target genes. To study how the interactions of AP-1 proteins with those within, as well as across the families determine cellular responses, we are using our BiFC assays, in combination with molecular, cellular, biochemical, and genetic approaches, to visualize these interactions in living cells and to investigate the regulation and functional consequences of the interactions. Our current projects include:
Regulation of ATF2 subcellular localization and transcriptional activity by its dimerization partner c-Jun.
Molecular mechanisms of ATF2 in conferring the resistance of cancer cells and cancer stem cells to chemotherapy and radiation.
Role of cross-family interactions of NF-κB with AP-1 in the acquisition of chemoresistance and radioresistance.
Screening of small molecules for the inhibition of protein-protein interactions using a multicolor BiFC-based HTS system.
AP-1 in C. elegans development: Gene targeting has been widely used to study the functions of genes in vivo. However, problems often encountered using gene knock-out studies are embryonic lethality or lack of obvious phenotypes. The former prevents further evaluation of the targeted genes during the entire developmental process and the latter frequently reflects functional redundancy of homologous genes or isoforms. Because AP-1 functions as heterodimers or homodimers, the regulation of dimer formation plays a pivotal role in the control of their transcriptional activities. Accordingly, monitoring their interactions throughout development will provide a substantial link to the roles of AP-1 in development. The establishment of the BiFC assays has endowed us with a unique way to study protein-protein interactions in living animals. We are applying the BiFC assays to study the temporal and spatial interactions of C. elegans AP-1 proteins in living worms. This project is currently supported by the National Science Foundation.
Representative Publications
Liu, H., Deng, X., Shyu, Y., Li, J.J., Taparowsky, EJ., and Hu, C.-D. Mutual regulation of c-Jun and ATF2 by transcriptional activation and subcellular localization. The EMBO Journal, in press.
Wang ,KZQ, Wara-Asparati, N., Boch, J.A., Yoshida, Y., Hu, C.-D., Galson, D.L., and Auron, P.E. TRAF6 activation of PI3 kinase-dependent cytoskeletal changes is cooperative with Ras and mediated by an interaction with cytoplasmic c-Src. J. Cell Sci., in press.
Shyu, Y., Liu, H., Deng, X., and Hu, C.-D. Identification of new fluorescent fragments for BiFC analysis under physiological conditions. BioTechniques, 40:61-66 (2006).
Hu, C-D., Grinberg A., and Kerppola T. Visualization of protein interaction in living cells using bimolecular fluorescence complementation (BiFC) analysis. Current Protocol in Cell Biology. 21.3.1-21.3.21 (2005).
Hu, C-D. and Kerppola TK. Direct visualization of protein interactions in living cells using bimolecular fluorescence complementation analysis. Protein-Protein Interactions (ed. P. Adams and E. Golemis), Cold Spring Harbor Laboratory Press (2005).
Grinberg A, Hu, C.-D., and Kerppola T. Visualization of Myc/Max/Mad family dimers and the competition for dimerization in living cells. Mol. Cell. Biol. 24, 4294-4308 (2004).
Hu, C.-D. and Kerppola, T. Simultaneous visualization of interactions between multiple proteins in living cells using multicolor bimolecular fluorescence complementation analysis. Nat. Biotechnol. 21, 539-545 (2003).
Hu, C.-D. Chinenov, Y., and Kerppola, T. Visualization of interactions among bZIP and Rel family proteins in living cells using bimolecular fluorescence complementation. Mol. Cell. 9, 789-798 (2002).
Song*, C., Hu*, C.-D., Masago, M., Kariya, K., Yamawaki-Katatoka, Y., Shibatohge, M., Sen, H., Wu, D., Satoh, T., and Kataoka, T. Regulation of a novel human phospholipase C, PLC-ε through differential membrane targeting by Ras and Rap1 J. Biol. Chem. 276, 2752-2757 (2001).
*Equal contribution to this work
Liao, Y., Kariya, K., Hu, C.-D., Shibatohge, M., Goshima, M., Okada, T., Watari, Y., Gao, X., Jin, T.-G., Yamawaki-Katatoka, Y., and Kataoka, T. RA-GEF, a novel Rap1A guanine nucleotide exchange factor containing a Ras/Rap1A-associating domain, is conserved between nematode and humans. J. Biol. Chem. 274, 37815-37820 (1999).
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