FBXW7促进GATA3降解的分子机制及其在乳腺癌中生物学意义的研究

The transcription factor GATA3 is a key regulator of mammary gland development and a definitive marker of luminal breast cancer. In our previous work, we demonstrated that GATA3 promoted breast cancer cell proliferation and tumorigenesis through physically and functionally associated with poly-ADP ribose polymerase-1 (PARP1). Our results unveiled a molecular basis for the coordinated regulation between GATA3 and PARP1 in transcription activation, providing a mechanism for GATA3 in breast carcinogenesis. However, the molecular mechanisms that control GATA3 stability in physiological or pathological state is still not understood. In our current work, we generated a mammary carcinoma MCF-7 cell line that stably expresses FLAG-tagged GATA3. Immunopurification of GATA3 from MCF-7 cell extracts with anti-FLAG and analysis of the GATA3-containing protein complex by mass spectrometry revealed that GATA3 is associated with PARP1 as well as with several other proteins including an F-box protein FBXW7 (F-box and WD repeat domain-containing 7), the substrate recognition component of an evolutionary conserved SCF (complex of SKP1, CUL1 and F‑box protein), which is also a well characterized tumor suppressor linked to multiple human malignancies. Furthermore, we confirmed that FBXW7 physically interacts with GATA3 by co-immunoprecipitation. We showed that FBXW7 promotes GATA3 degradation through the proteasome dependent pathway. Moreover, we found that FBXW7 promoted GATA3 ubiquitination in vivo. These preliminary results indicated that FBXW7 plays an important role in GATA3 stability through proteasome-ubiquitination pathway. But the underlying mechanism of how FBXW7 regulate GATA3 in the protein level and the biological significance of GATA3 destabilization by FBXW7 need to be further elucidated. We will focus on finding out the pivotal upstream as well as downstream signaling sensors or transducers of the FBXW7-GATA3 axis in breast cancer. We envision that the further understanding of the molecular mechanisms through which FBXW7 orchestrates GATA3 level, in combination with the identification of the upstream triggers and downstream effectors in the specific FBXW7-GATA3 axis will aid the understanding of the regulation of breast cancer progression, guide new approaches development and benefit the therapeutic pursuits for human cancer.

转录因子GATA3是乳腺细胞分化的重要调节因子，同时也是乳腺导管癌的标记分子。过去工作中，我们发现GATA3通过与多聚ADP核糖聚合酶1（poly-ADP ribose polymerase-1, PARP1）协同作用促进乳腺癌细胞的增殖。但在生理及病理状态下GATA3蛋白水平调节的分子机制仍是不清楚的。近期工作中，我们发现GATA3可与肿瘤抑制蛋白FBXW7(F-box and WD repeat domain-containing 7)相互作用。接下来我们证明了FBXW7可以通过泛素-蛋白酶体途径降解GATA3。未来研究中，我们将进一步探索FBXW7调节GATA3蛋白水平的分子机制以及其在乳腺癌发生发展中的作用，同时将深入阐明FBXW7-GATA3作用通路中关键性的上下游分子事件，以期在将来研究中为乳腺癌的治疗提供可能的靶点和治疗方向。..

GATA3是细胞命运决定中的关键转录因子，其失调与各种类型的恶性肿瘤有关。但是GATA3是如何被调节以及其功能的研究尚不清楚。在该研究中，我们报导了GATA3和FBXW7α存在物理上的联系。FBXW7α通过SKP1-CUL1-F-box E3连接酶复合体降解GATA3。更重要的是，我们表明了FBXW7α是通过GSK3依赖的途径泛素化并降解GATA3的。进一步，我们揭示了FBXW7α通过不稳定GATA3来抑制乳腺癌细胞的生存能力。另外，在乳腺癌样本中，FBXW7α和GATA3的表达呈负相关性。这一研究表明了FBXW7α是一个很重要的GATA3的负调节因子。同时，也揭示了在乳腺癌细胞中GATA3丰度调节的一条途径。