Negative transcriptional regulatory mechanisms of cytokine LD78 which regulates hematopoiesis

从几个方面的证据来看，似乎沉默元件抑制趋化因子LD 78基因在没有发现信息的细胞中的表达，我们试图鉴定和纯化与沉默元件和ICK-1元件结合的转录调节因子。ICK-1元件存在于启动子中，并且正和负调节LD 78转录。然而，这些转录调控因子非常不稳定，因此很难纯化。我们还分析了趋化因子家族成员MCP-3的启动子。MCP-3启动子在HeLa细胞中有活性，但没有发现MCP-3的信息传递，由于趋化因子基因簇集在人17号染色体上，抑制LD 78表达的沉默元件可能也抑制MCP-3和其他趋化因子基因的表达。因此，我们构建了一个酵母人工染色体（YAC）重叠群的几个Mb长含有所有的趋化因子基因染色体17q11.2。该重叠群还包含4个趋化因子样基因，已在GenBank中以EST形式保藏。该YAC重叠群除了沉默元件的分析之外，还可用于鉴定新的趋化因子基因。

From several lines of evidence, it seems likely that a silencer element inhibits chemokine LD78 gene expression in the cells where no message is found. We have tried to identify and purify the transcriptional regulators which bind to this silencer element and to the ICK-1 element. The ICK-1 element is present in the promoter and regulates the LD78 transcription positively and negatively. However, These transcriptional regulators are very unstable and therefore it was difficult to purify them. We also analyzed the promoter of a chemokine family member MCP-3. MCP-3 promoter was active in HeLa cells, although no MCP-3 message was found. Since chomkines genes are clustered on human chromosome 17, the silencer element which inhibits the LD78 expression may also repress the expression of MCP-3 and other chemokine genes. We therefore constructed a yeast artificial chromosome (YAC) contig of several Mb long containing all chemokine genes present on chromosome 17q11.2. The contig also contains four chemokine-like genes which were deposited in GenBank as ESTs. This YAC contig is useful for identification of new chemokine genes in addition to the analysis of the silencer element.