生物谷报道：目前临床治疗癌症比较有效的方法主要是手术切除和放化疗，其中放化疗是大部分患者都要经历的，但是经过放化疗的医治依然还是会有残留一些癌细胞，近期来自普度大学的研究人员发现了一个也许在癌细胞抵御放化疗再生作用中起到关键作用的机制
（蛋白），而且这一机制也许同样在阿滋海默症和心脏疾病中起作用。这一研究成果发表在近日出版的EMBO J上。
利用一种由普度大学发明的新型成像技术，华人科学家Chang-Deng Hu博士和其他研究人员发现之前认为存在于健康细胞核的一种蛋白实际上可以在细胞核和细胞质之间穿梭，而且这种蛋白的穿梭作用是由细胞核中比邻的另外一种蛋白调控的。这两种蛋白就是c-Jun和ATF2（AP-1蛋白复合物重要组成蛋白）。
AP-1：activating protein-1，这种转录因子主要由Jun、Fos、ATF及JDP亚家族组成, 亚家族单体以同源（homodimers）或异源二聚体（heterodimers）的形式结合DNA靶序列, 调节靶基因，在细胞的正常生长和癌性转化过程中起着重要作用。AP-1的活性受多种核因子调节，同时单体间也存在相互促进或拮抗作用。AP-1对各种刺激如应激、辐射或生长信号等作出生理或病理应答, 参与细胞的增殖、分化和转化等过程, 在肿瘤的形成、转移和侵袭中发挥重要作用, 已经有学者研究通过抑制AP-1活性来发展抗肿瘤药物.
目前一般都认为健康细胞中的AP-1都是定位在细胞核中的，然而Chang-Deng Hu等研究人员通过F9小鼠畸形癌细胞系实验发现ATF2蛋白有出核与入核结构信号（“nuclear export” and “uclear localization” signals），即能够从细胞核到细胞质，也能从细胞质回到细胞核。而且研究人员也发现当核内ATF2与c-Jun形成异源二聚体的时候，穿膜信号就会被封闭，ATF2就不能穿过核膜到细胞质中了。
临床放化疗手段主要是通过引发ATF2表达来治疗癌症，但是根据实验结果，Chang-Deng Hu认为这样过量表达出来的ATF2由细胞核内c-Jun不足，因此会大量积累到细胞质中，而且除了观察到小鼠肿瘤干细胞中有ATF2的积累，研究人员还发现将这些细胞暴露在紫外光中会引起c-Jun蛋白的表达，与ATF2结合后导致穿梭过程的停止，细胞死亡。
之前的研究证明ATF2的过量表达会引起癌细胞对放化疗的抵制，因此ATF2的穿梭机制也许在癌症细胞抵御机理中起到重要的作用，通过阻止ATF2从细胞核转移到细胞质也许可以有效的增加癌症治疗的有效性。
原始出处:
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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延伸阅读：有关ATF和c-JUN的关系
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
简介：
Chang-Deng Hu
主页: http://people.pharmacy.purdue.edu/~cdhu/
1984年，就读于安徽 蚌埠医学院（Bengbu Medical College）（美国认可的中国医学院校之一）；
1987年，获得同济医科大学肿瘤免疫学硕士学位；
1997年，获得日本神户大学（Kobe University）分子生物学博士学位；
1997年-2000年，日本神户大学Assitant Professor；
2000年-2002年，美国密歇根大学博士后；
2002年-2003年，美国密歇根大学研究员；
2003年-至今，美国普度大学Assistant Professor of Medicinal Chemistry and Moleculary Pharmacology，
印第安纳州Walther Cancer Institute研究员
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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