E1A-CtBP interactions in oncogenic transformations

描述（由申请人提供）：腺病毒E1A c端CR4区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作为转录辅抑制因子，在脊椎动物的发育、肿瘤发生和细胞凋亡调控中发挥关键作用。它们在若干发展过程中是功能冗余的，同时对某些其他进程发挥独特的作用。CtBP2是高度核性的，CtBP1是核性和细胞质性的。ctbp通过募集几种组蛋白修饰酶成分（如组蛋白去乙酰化酶、甲基转移酶和组蛋白去甲基化酶）介导序列特异性转录抑制。此外，CtBP蛋白复合物还含有介导蛋白质SUMO修饰的E2和E3酶。缺乏与ctbp相互作用的腺病毒E1A突变体表现出与Ras癌基因合作的超转化表型。表达E1A CR4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。我们假设E1A与CtBP的相互作用可能会调节与E1A n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CtBP靶基因的模式发生显著变化。在Aim 1中，我们将确定E1A c端CR4区域和ctbp对E1A n端区域Ras癌基因协同活性的影响。目的2将阐明CtBP2独特的转录活性，并确定E1A对CtBP2介导的细胞靶基因表达调控的影响。目的3将确定E1A对CtBP1细胞质和细胞核功能的影响。目的4将阐明ctbp相关的SUMOylation机制在转录抑制中的作用。

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.