E1A-CtBP interactions in oncogenic transformations

描述(申请人提供)：腺病毒E1AC端CR4区域通过高度保守的序列基序PLDLS与细胞CtBP家族蛋白CtBP1和CtBP2相互作用。CtBP1和CtBP2是转录抑制因子，在脊椎动物的发育、肿瘤发生和细胞凋亡调控中发挥重要作用。它们在几个发展过程中在功能上是多余的，同时在某些其他过程中发挥独特的活动。CtBP2是高度有核的，CtBP1既是核的，也是胞质的。CtBPs通过组蛋白脱乙酰酶、甲基转移酶和组蛋白去甲基酶等组蛋白修饰酶组分的募集，介导序列特异性转录抑制。此外，CtBP蛋白复合体还包含E2和E3酶，它们介导蛋白质的相扑修饰。与CtBPs缺乏相互作用的腺病毒E1a突变体表现出与RAS癌基因协同的高转化表型。表达E1ACR4突变体和RAS癌基因的转化细胞具有高度的致瘤性和转移性。我们推测，E1a与CtBP的相互作用可能调节与E1a的N-末端区域相关的细胞蛋白的活性。此外，E1a与CtBP的相互作用也可能导致细胞内CtBP靶基因模式的显著变化。在目标1中，我们将确定E1AC-末端CR4区域和CtBPs对E1AN-末端区域RAS癌基因协同活性的影响。目的2阐明CtBP2独特的转录活性，并确定E1a在CtBP2介导的细胞靶基因表达调控中的作用。目的3确定E1a对CtBP1胞浆和核功能的影响。目的4将阐明CtBP相关的SUMO化机制在转录抑制中的作用。 与公共卫生的相关性：大约三分之一的人类癌症包含RAS癌基因的致癌突变。同样，Myc癌基因在人类恶性肿瘤中也起着主导作用。E1a和Myc共有的某些功能协同RAS的致癌转化，而E1a和CtBP的相互作用则拮抗这种活性。我们拟议的研究将利用从病毒癌蛋白E1a研究中获得的知识，以揭示控制肿瘤发生的潜在新机制，并提出抑制人类这一过程的策略。

DESCRIPTION (provided by applicant): Adenovirus E1A C-terminal CR4 region interacts with the cellular CtBP family proteins, CtBP1 and CtBP2 through a highly conserved sequence motif, PLDLS. CtBP1 and CtBP2 function as transcriptional corepressors and play critical roles during development, oncogenesis and apoptosis regulation in vertebrates. They are functionally redundant for several developmental processes while exerting unique activities with regard to certain other processes. CtBP2 is highly nuclear and CtBP1 is both nuclear and cytosolic. The CtBPs mediate sequence specific transcriptional repression by recruitment of several histone modifying enzymatic constituents such as histone deacetylases, methyl transferases and a histone demethylase. Additionally, the CtBP protein complex also contains E2 and E3 enzymes that mediate SUMO modification of proteins. Adenovirus E1A mutants deficient in interaction with CtBPs exhibit a hyper-transforming phenotype in cooperation with the Ras oncogene. The transformed cells expressing E1A CR4 mutant and the Ras oncogene are highly tumorigenic and metastatic. We hypothesize that interaction of E1A with CtBP might modulate the activities of cellular proteins associated with the N-terminal region of E1A. Additionally, interaction of E1A with CtBP might also cause significant changes in the pattern of cellular CtBP target genes. In Aim 1, we will determine the effects of E1A C-terminal CR4 region and CtBPs on the Ras oncogene cooperating activity of the E1A N-terminal region. Aim 2 will elucidate the unique transcriptional activities of CtBP2 and to determine the effect of E1A on CtBP2- mediated regulation of expression of cellular target genes. Aim 3 will determine the effect of E1A in the cytosolic and nuclear functions of CtBP1. Aim 4 will elucidate the role of CtBP-associated SUMOylation machinery in transcriptional repression. Relevance to Public Health: About one third of all human cancers contain oncogenic mutations in the Ras oncogene. Similarly, the Myc oncogene also plays a dominant role in human malignancies. Certain functions shared by E1A and Myc cooperate with Ras oncogenic transformation while interaction of E1A with CtBP antagonizes such activity. Our proposed studies will harness the knowledge gained from the study of the viral oncoprotein E1A to unravel potential new mechanisms governing oncogenesis and suggest strategies to inhibit the process in humans.