Gadd 45 genes sensors of stress and tumor modulators

描述（由申请人提供）：Gadd 45基因（a，B，g）是调节细胞对遗传毒性/生理应激的反应并调节肿瘤形成的应激传感器。Gadd 45蛋白与其他应激反应蛋白相互作用，包括PCNA、p21、Cdc 2/CyclinB 1、MEKK 4和p38激酶。Gadd 45蛋白质的功能在多大程度上重叠，以及应激刺激的性质如何决定Gadd 45功能以信号细胞存活或细胞死亡尚不清楚。所测试的假设是，应激的性质/幅度决定了Gadd 45蛋白将与哪种配偶体相关联以发出细胞存活或细胞死亡的信号。在低应激时，Gadd 45蛋白可能与p21、cdc 2/cyclinB 1和PCNA相互作用，激活细胞周期停滞和DNA修复，促进细胞存活;而在高应激时，包括细胞衰老和激活的癌基因，Gadd 45蛋白可能与应激激酶（MEKK 4、p38、JNK）相互作用，促进细胞凋亡或衰老。推测Gadd 45蛋白的应激感应功能在调节肿瘤形成中起作用。产生了一个或多个gadd 45基因缺陷的小鼠& Gadd 45突变蛋白与特定伴侣结合缺陷的小鼠来测试这一假设。目的1将评估Gadd 45和相互作用伴侣在细胞对不同剂量的遗传毒性应激反应中的作用。将测试在暴露于低/高水平的遗传毒性应激后，Gadd 45缺陷对体外和体内gadd 45 KO和WT细胞中的细胞周期停滞、存活或凋亡的影响。此外，Gadd 45/伴侣蛋白相互作用的作用将通过测试转导的wt/突变gadd 45基因拯救wt表型的能力来探索。目的2将评估Gadd 45及其伴侣在MEFs对生理/致癌应激的反应中的作用。Gadd45a-/- & 发现gadd 45 g-/- MEFs逃避复制和癌基因介导的衰老，而gadd 45 b-/- MEFs失去活力。Gadd 45 a-/-和gadd 45 g-/- MEFs也被发现对ras转化敏感，而gadd 45 a/gadd 45 g双KO MEFs对ras或myc的转化敏感。将探讨Gadd 45和相互作用的伙伴在衰老，生存和转化易感性中的作用。目的3探讨gadd 45基因作为肿瘤发生调节因子的功能。产生乳腺癌易感性MMTV-ras和MMTV-myc小鼠wt或gadd 45 a无效。Gadd 45 a缺陷促进了MMTV-ras肿瘤的形成，但延缓了MMTV-myc的致癌作用，表明Gadd 45 a依赖于癌基因而起肿瘤促进/抑制作用。实验的目的是评估gadd 45基因在差异调节ras/myc驱动的乳腺肿瘤发生中的应激反应功能。所获得的数据对于更好地理解压力传感器在肿瘤发生中的作用以及癌症治疗中的治疗抗性如何产生和消除将具有重要意义。

DESCRIPTION (provided by applicant): Gadd45 genes (a, b, g) are stress sensors that modulate the response of cells to genotoxic/physiological stress, & modulate tumor formation. Gadd45 proteins interact with other stress response proteins, including PCNA, p21, Cdc2/CyclinB1, MEKK4 & p38 kinase. To what extent the functions of Gadd45 proteins overlap, & how the nature of stress stimuli dictate Gadd45 functions to signal cell survival or cell death is unclear. The hypothesis tested is that the nature/magnitude of stress dictates which partners Gadd45 proteins will associate with to signal cell survival or cell death. In response to low stress Gadd45 proteins may interact with p21, cdc2/cyclinB1 & PCNA to activate cell cycle arrest and DNA repair to promote cell survival, whereas in response to high stress, including cellular aging & activated oncogenes, Gadd45 proteins may interact with stress kinases (MEKK4, p38, JNK) to promote apoptosis or senescence. It is surmised that stress sensing functions of Gadd45 proteins play a role in modulating tumor formation. Mice deficient for one or more gadd45 genes & Gadd45 mutant proteins deficient in binding to particular partners were generated to test the hypothesis. Aim 1 will assess the role of Gadd45 & interacting partners in the response of cells to varying doses of genotoxic stress. The effect of Gadd45 deficiencies on cell cycle arrest, survival or apoptosis in gadd45 KO & WT cells in vitro & in vivo, following exposure to low/high levels of genotoxic stress will be tested. Also, the role of Gadd45/partner protein interactions will be explored by testing the ability of transduced wt/mutant gadd45 genes to rescue wt phenotypes. Aim 2 will assess role of Gadd45 & partners in the response of MEFs to physiological/oncogenic stress. Gadd45a-/- & gadd45g-/- MEFs were found to escape replicative & oncogene mediated senescence, whereas gadd45b-/- MEFs lose viability. Gadd45a-/- & gadd45g-/- MEFs were also found to be susceptible to ras transformation, whereas gadd45a/gadd45g double KO MEFs were susceptible for transformation by ras or myc. The role Gadd45 & interacting partners play in senescence, survival & susceptibility to transformation will be explored. Aim 3 will assess function of gadd45 genes as modulators of tumor development. Breast cancer prone MMTV-ras & MMTV-myc mice wt or null for gadd45a were generated. Gadd45a deficiency accelerated MMTV-ras tumor formation, yet retarded MMTV-myc carcinogenesis, indicating that gadd45a functions as tumor promoter/suppressor depending on the oncogene. Experiments are targeted at assessing the role stress response functions of gadd45 genes play in differentially modulating ras/myc driven breast tumorigenesis. Data obtained will be of great importance to better understand the role of stress sensors in tumorigenesis, & how treatment resistance in cancer therapy can arise & be abrogated.