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

p53转录因子由肿瘤抑制基因编码，该基因在超过50%的所有癌症中突变。我们鉴定了14-3-3sigma基因作为p53的直接靶点，p53介导了人癌细胞系DNA损伤后G2/M期进展的阻断。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生物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Cre等位基因在成年小鼠中进行14-3-3sigma。这种方法将模拟14-3-3sigma的表观遗传失活，这通常发生在肿瘤形成期间。此外，将分析急性14-3- 3 σ失活对皮肤化学致癌作用的影响以及14-3- 3 σ与肠道中p53介导的DNA损伤反应的相关性。此外，14-3-3sigma的丢失和癌基因激活之间的潜在合作将被研究。敲除另外两个p53靶基因p21和p53 A，在没有额外的应激（如DNA损伤）的情况下也不会导致明显的表型。我们将产生14-3-3sigma、p21和p53 A缺陷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损伤反应的联合作用。ER（反复脱毛）小鼠品系在14-3-3sigma基因中携带引起表皮过度增殖的点突变。将比较ER突变和14-3- 3 σ缺失在FVB背景下的功能后果，因为我们的结果表明14-3- 3 σ的ER mut可能不仅仅代表功能缺失突变。总之，这些研究将为理解14-3-3sigma在生理学和病理生理学中的功能做出重要贡献。

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.