Analysis of organismal and tumor suppressive functions of 14-3sigma

P53转录因子是由一种肿瘤抑制基因编码的，该基因在超过50%的癌症中发生突变。我们发现14-3-3sigma基因是P53的直接靶点，P53在DNA损伤后通过G2/M期抑制肿瘤进展。在肿瘤中，14-3-3sigma基因经常被CpG甲基化沉默。然而，14-3-3sigma失活与癌症形成及其机体功能的相关性尚不清楚。在这里，我建议在几种组织和细胞类型中使用条件性Cre等位基因来灭活成年小鼠的14-3-3sigma。这种方法将模仿肿瘤形成过程中常见的14-3-3西格玛的表观遗传失活。此外，还将分析14-3-3sigma的急性失活对皮肤化学致癌的影响，以及14-3-3sigma与肠道中P53介导的DNA损伤反应的相关性。此外，还将研究14-3-3sigma缺失与癌基因激活之间的潜在协同作用。另外两个p53靶基因p21和PUMA的敲除也不会在没有额外压力的情况下产生明显的表型，就像DNA损伤一样。我们将建立14-3-3sigma、p21和PUMA缺失的复合基因敲除小鼠，以确定这些缺失对P53介导的肿瘤抑制和DNA损伤反应的联合影响。ER(重复脱毛)小鼠品系携带14-3-3sigma基因的点突变，导致表皮过度增殖。我们将比较ER突变和14-3-3sigma缺失在FVB背景下的功能后果，因为我们的结果表明，14-3-3sigma的ER mut可能不仅仅代表功能突变的丧失。综上所述，这些研究将为理解14-3-3sigma的生理学和病理生理学功能提供重要的贡献。

The p53 transcription factor is encoded by a tumor suppressor gene which is mutated in more than 50% of all cancers. We identified the 14-3-3sigma gene as a direct target of p53 which mediates inhi-bition of progression through the G2/M phase following DNA damage in a human cancer cell line. In tumors the 14-3-3sigma gene is frequently silenced by CpG-methylation. However, the relevance of 14-3-3sigma inactivation for cancer formation and its organismal function is not known. Here I propose to inactivate 14-3-3sigma in adult mice using conditional Cre alleles in several tissues and cell types. This approach will mimic the epigenetic inactivation of 14-3-3sigma which commonly happens during tumor formation. Furthermore, the effect of acute 14-3-3sigma inactivation on chemical carcinogenesis of the skin and the relevance of 14-3-3sigma for the p53-mediated DNA damage response in the intestinal tract will be analysed. In addition, the potential co-operation between loss of 14-3-3sigma and oncogene activation will be studied. The knock-out of two other p53-target genes, p21 and PUMA, also does not lead to an obvious phenotype without additional stress, as DNA damage. We will generate compound knock-out mice deficient for 14-3-3sigma, p21 and PUMA in order to determine the combined effect of these deletions on the p53-mediated tumor suppression and DNA damage response. The ER (repeated epilation) mouse strain carries a point mutation in the 14-3-3sigma gene which causes epidermal hyper-proliferation. The functional consequences of the ER mutation and 14-3-3sigma deletion on a FVB background will be compared, as our results indicate that the ER mut of 14-3-3sigma may not simply represent a loss of function mutation. In summary, these studies will provide an important contribution to the understanding of 14-3-3sigma function in physiology and patho-physiology.