ACCESSORY CELL ACTIVATION OF THE IMMUNE RESPONSE

单核细胞至少表达两类不同类型的细胞特异性基因。一类以M-CSF受体基因c-FMS为例，是结构性表达的，并依赖于分化状态。另一类，以IL-1β基因(Il1b)为代表，一般也是单核细胞特异性的，但只有在刺激事件平行于静止的单核细胞转化为激活的单核/巨噬细胞时才会立即表达。对il1b调控机制的研究发现，该基因有两个不同的可分离区域，分别对应于两个标准，一个是细胞类型特异的143bp基本启动子，另一个是信号响应上游增强子。增强子的功能依赖于几个广泛表达的信号响应转录因子(如C/EBPbeta、CREB、c-jun和NF-kappaB)的协同功能，其中包括一个新的STAT样因子，而71个碱基启动子似乎依赖于单髓因子SPI-1/PU.1(SPI-1)的一个分子的结合，SPI-1在单核细胞发育和细胞类型特异性基因表达中起关键作用。基本启动子和增强子之间的功能相互作用需要一个关键的额外73bp元件，该元件需要额外的SPI-1分子结合。在存在巨细胞病毒蛋白IE2的情况下，该元件不是增强非依赖于启动子的活性所必需的。IE2似乎直接与SPI-1ETS结构域相互作用。该区域在所有ETS蛋白中都存在，并与广泛的其他蛋白质相互作用，调节双方的功能。本研究的目的是阐明SPI-1与其他蛋白质相互作用的机制，并将增强子功能整合到核心启动子中，并试图克隆新的STAT样因子，该因子可在内毒素、IL-1和IL-6的作用下被激活。

Monocytes express at least two different classes of cell-type specific genes. One class, exemplified gy the M-CSF receptor gene, c-fms, is constitutively expressed and dependent upon the differentiated state. Another class, represented by the IL-1beta gene (il1b), is also generally monocyte-specific, but is only expressed immediately in response to a stimulation event that parallels the conversion of the resting monocyte to the activated monocyte/macrophage. Investigation of the il1b regulation mechanisms have revealed two distinct and separable regions of the gene that correspond to each of the two criteria, a cell type specific 143bp basal promoter and a signal-responsive upstream enhancer. The enhancer function depends upon the cooperative function of several broadly expressed signal-responsive transcription factors (e.g., C/EBPbeta, CREB, c-Jun, and NF- kappaB), including a novel STAT-like factor, whereas the 71 bp basal promoter appears to depend upon binding of one molecule of the mono-myeloid factor Spi-1/PU.1 (Spi-1), a factor that plays a central key role in monocyte development and cell type-specific gene expression. The functional interaction between the basal promoter and an enhancer requires a critical additional 73bp element that requires the binding of an additional Spi-1 molecule. This element is not required for enhancer-independent activity in the presence of IE2, a cytomegalovirus protein. IE2 appears to interact directly with the Spi-1 ETS domain. This region is found in all ETS proteins and mediates associations with a broad range of other proteins, modulating function in both partners. The object of this proposal is to elucidate the mechanism by which Spi-1 interacts with other proteins and integrates enhancer function into the core promoter and to attempt to clone the novel STAT-like factor that is activated in response to LPS, IL-1, and IL-6.