TRANSCRIPTIONAL REGULATION OF C-FOS

c-fos的转录调控将作为一种方法进行研究 对理解细胞的信号传导途径有很大帮助。 c-fos的转录被生长因子和其他因子快速诱导， 影响细胞生长和分化的药剂。 生长因子结合 细胞表面的受体，但大多数随后的 导致c-fos表达增加的生化步骤， 细胞分裂还不清楚。 不正确的c-fos表达可导致 细胞的癌变和信号的异常控制 转导途径也可能导致肿瘤发生。 因此， 对这些途径的分析对于理解和治疗 癌症。 c-fos启动子中血清和表皮生长的关键元件 调节因子是血清反应元件（SRE）。 该规例 可能由血清反应因子（SRF）介导， 特别是SRE。 三种方法将被用来分析监管 通过SRF。 1)SRF的磷酸化作为一种调节性修饰， 追究 由于c-fos的表达是在 蛋白质合成抑制剂，翻译后修饰必须 参与监管。 SRF在体内被磷酸化，这 修饰是体外DNA结合活性所必需的。 2)在 具有粗品和纯化组分的体外转录系统将是 用于测定SRF转录活性的变化。 这 活性似乎与其DNA结合分开调节 活动 3)SRF可能受到蛋白质的正调控或负调控 这些与SRF稳定结合的蛋白质将被 通过它们与SRF的共纯化或共免疫沉淀来寻找。 细胞钙水平的变化可能在生长中起重要作用 调控 c-fos的钙调节不依赖于SRE， 似乎利用帽位点下游的序列元件。 的 将绘制钙反应元件，结合 它将被确定，和调节的生化机制， 通过这些序列元素和因素将被研究。

The transcriptional regulation of c-fos will be studied as a method towards understanding the signal transduction pathways of the cell. Transcription of the c-fos is induced rapidly by growth factors and other agents that affect cell growth and differentiation. Growth factors bind to their receptors on the cell surface, yet most of he subsequent biochemical steps that lead to increased c-fos expression and ultimately cell division are not understood. Incorrect c-fos expression can cause the cancerous transformation of cells and aberrant control of the signal transduction pathways may also lead to oncogenesis. Thus, a detailed analysis of these pathways is crucial to the understanding and treatment of cancer. The key element in the c-fos promoter for serum and epidermal growth factor regulation is the serum response element (SRE). the regulation is likely to be mediated by the serum response factor (SRF) which binds specifically to SRE. Three approaches will be used analyze regulation through SRF. 1) Phosphorylation of SRF as a regulatory modification will be investigated. Since c-fos expression is induced in the presence of protein synthesis inhibitors, post-translational modifications must be involved in the regulation. SRF is phosphorylated in vivo and this modification is required for the DNA binding activity in vitro. 2) In vitro transcription systems with crude and purified components will be utilized to assay for changes n SRF's transcriptional activity. This activity appears to be regulated separately from its DNA binding activity. 3) SRF may be regulated positively or negatively by proteins which complex with it. Such proteins which stably bind to SRF will be sought by their copurification or co-immunoprecipitation with SRF. Changes in cellular calcium levels may play an important part in growth regulation. Calcium regulation of c-fos is independent of SRE and appears to utilize sequence elements downstream of the cap site. The calcium response element(s) will be mapped, nuclear factor(s) which bind to it will be identified, and the biochemical mechanism of regulation through these sequence elements and factors will be investigated.