Gadd 45 genes sensors of stress and tumor modulators

描述（由申请人提供）：Gadd45基因（a, b, g）是应激传感器，可调节细胞对基因毒性/生理应激的反应，并调节肿瘤的形成。Gadd45蛋白与其他应激反应蛋白相互作用，包括PCNA、p21、Cdc2/CyclinB1、MEKK4和p38激酶。Gadd45蛋白的功能在多大程度上重叠，以及应激刺激的性质如何决定Gadd45功能来指示细胞存活或细胞死亡尚不清楚。经过测试的假设是，压力的性质/大小决定了Gadd45蛋白将与哪些伙伴联系起来，以发出细胞存活或死亡的信号。在低应激条件下，Gadd45蛋白可与p21、cdc2/cyclinB1和PCNA相互作用，激活细胞周期阻滞和DNA修复，促进细胞存活，而在高应激条件下，包括细胞衰老和活化的癌基因，Gadd45蛋白可与应激激酶（MEKK4、p38、JNK）相互作用，促进细胞凋亡或衰老。推测Gadd45蛋白的应激感应功能在调控肿瘤形成中发挥作用。产生缺乏一个或多个gadd45基因的小鼠和缺乏与特定伴侣结合的gadd45突变蛋白来验证这一假设。目的1将评估Gadd45及其相互作用伙伴在细胞对不同剂量的基因毒性应激的反应中的作用。将测试Gadd45缺乏对体外和体内暴露于低/高水平基因毒性应激后的Gadd45 KO和WT细胞周期阻滞、存活或凋亡的影响。此外，通过测试转导的wt/突变Gadd45基因挽救wt表型的能力，将探索Gadd45/伴侣蛋白相互作用的作用。目的2将评估Gadd45及其伴侣在mef对生理/致癌应激的反应中的作用。研究发现，Gadd45a-/-和gadd45g-/- mef可以逃避复制性和癌基因介导的衰老，而gadd45b-/- mef则失去生存能力。Gadd45a-/-和gadd45g-/- mef也被发现易受ras转化，而Gadd45a /gadd45g双KO mef易受ras或myc转化。Gadd45及其相互作用伙伴在衰老、生存和易感性转化中的作用将被探讨。目的3将评估gadd45基因作为肿瘤发展调节剂的功能。产生具有乳腺癌易感性的MMTV-ras和MMTV-myc小鼠，gadd45a缺失或缺失。Gadd45a缺乏加速了MMTV-ras肿瘤的形成，但却延缓了MMTV-myc的癌变，这表明Gadd45a根据癌基因发挥肿瘤启动子/抑制子的作用。实验旨在评估gadd45基因的应激反应功能在ras/myc驱动的乳腺肿瘤发生中的差异调节作用。获得的数据对于更好地理解应力传感器在肿瘤发生中的作用以及癌症治疗中如何产生和消除治疗耐药性具有重要意义。

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.