Analysis of regulation of carcinogenesis by the BCAP-binding molecule BB1

我们已经证明，作为PI 3激酶结合分子分离的BCAP通过调节NF-κB家族成员c-Rel的丰度，有助于维持脾脏成熟B淋巴细胞的稳态。转录因子NF-κB诱导参与细胞凋亡、细胞周期和癌症转移的多种基因的表达。因此，阐明和调控NF-κB活性的信号对全面理解发病机制是必不可少的。为此，我们着手解开确保BCAP/NF-κB偶联的分子机制。通过使用含有Kb反应元件的报告基因构建体，显示含有富含脯氨酸的BCAP的C末端区域负责NF-κB活化。此外，BB 1被确定为该区域的酵母双杂交筛选的结合剂。siRNA介导的BB 1缺失导致NF-κB活性下降，表明BB 1参与NF-κ B调节信号。就BB 1的功能结构域而言，O端100个氨基酸区域是诱导NF-κ B活性所必需的。为了更详细地阐明BCAP的作用机制，我们还调查了其他结构相似的信号分子，这些分子可以构成BCAP家族，以进行比较。BANK是一种衔接蛋白，使用BLAST程序鉴定。我们建立了BANK缺陷小鼠，并揭示BANK通过共受体CD 40负调节信号，从而能够预防B淋巴细胞的高反应性。总的来说，我们认为BCAP家族成员的作用是将质膜上的分子事件转化为基因诱导，并抑制肿瘤发生。

We have demonstrated that BCAP, isolated as a binding molecule to PI3 kinase, contributes to maintenance of homeostasis of splenic mature B lymphocytes through regulation of the abundance of c-Rel, a member of the NF-κB familiy. The transcription factor NF-κB induces expression of a wide variety of genes involved in apoptosis, cell cycle and cancer metastasis. It is therefore is indispensable to clarify and manipulate signals modulating NF-κB activity toward a comprehensive understanding of onsogenesis. To this end, we set out to unravel the molecular machinery ensuring BCAP/NF-κB coupling. By using a reporter construct containing Kb-responsive elements, the C-terminal region of BCAP containing proline-rich stretches was shown to be responsible for NF-κB activation. Furthermore, BB1 was identified as a binder to this region by yeast two-hybrid screening. siRNA-mediated BB1 depletion gave rise to a drop of NF-κB activity, indicating BBl's involvement in NF-κB-modulating signals. In terms of functional domains within BB1, the Oterminal 100 amino-acid region was required for induction of NF-KB activity. To elucidate BCAP's mechanism of action in more detail, we also surveyed other signaling molecules with structural similarity, which could constitute the BCAP family, for comparison. BANK, an adaptor protein, was identified using the BLAST program. We established BANK-deficient mice and revealed that BANK negatively regulates signals via the co-receptor CD40, enabling prevention of hyper-responsiveness of B lymphocytes. Collectively, we propose that the BCAP family members operate to translate molecular events on the plasma membrane into gene induction, and serve to repress oncogenesis.