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首页> 外文期刊>Molecular and Cellular Biology >The adenovirus E1A-regulated transcription factor E4F is generated from the human homolog of nuclear factor phiAP3.
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The adenovirus E1A-regulated transcription factor E4F is generated from the human homolog of nuclear factor phiAP3.

机译：腺病毒E1A调节的转录因子E4F由核因子phiAP3的人类同源物产生。

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A 50-kDa cellular factor, E4F, has been implicated in mediating trans activation of the adenovirus E4 gene by the 289R E1A(13S) protein. Previous experiments demonstrated an E1A-dependent increase in E4F DNA binding activity, dependent on phosphorylation, that correlated with the activation of E4 transcription. Using expression screening, we isolated a cDNA clone encoding the E4F protein, as judged by DNA binding characteristics, transcriptional activation, and immunological criteria. The E4F-1 cDNA encodes a 783-amino-acid polypeptide that has 86% sequence identity with the murine nuclear factor phiAP3, a GLI-krüppel-related protein. E4F DNA binding activity is encoded within an amino-terminal region of E4F-1 that contains a zinc finger domain and, as with endogenous E4F, is phosphatase sensitive. We found that E4F was generated from the full-length E4F-1-encoded protein as a 50-kDa amino-terminal fragment. Moreover, E1A(13S) expression induced the phosphorylation of both forms of E4F-1 but differentially regulated their DNA binding activities, stimulating the 50-kDa fragment while reducing the activity of the full-length protein. In transient-transfection assays, the E4F-1 amino-terminal fragment stimulated the adenovirus E4 promoter in the presence of E1A(13S), whereas the full-length protein repressed the promoter in the absence, but not the presence, of E1A. The results indicate that the 50-kDa polypeptide responsible for E4F DNA binding activity is a fragment generated from the human homolog of phiAP3 and that the two forms of the E4F-1 protein are differentially regulated by E1A through phosphorylation.
机译：50 kDa的细胞因子E4F已被289R E1A（13S）蛋白介导了腺病毒E4基因的反式激活。先前的实验表明，依赖于E1A的E4F DNA结合活性的增加取决于磷酸化，这与E4转录的激活有关。使用表达筛选，我们分离出了一个编码E4F蛋白的cDNA克隆，通过DNA结合特征，转录激活和免疫学标准来判断。 E4F-1 cDNA编码一个783个氨基酸的多肽，与鼠核因子phiAP3（一种GLI-kruppel相关蛋白）具有86％的序列同一性。 E4F DNA结合活性在E4F-1的氨基末端区域编码，该区域包含一个锌指结构域，并且与内源性E4F一样，对磷酸酶敏感。我们发现E4F是由全长E4F-1编码的蛋白（50 kDa氨基末端片段）产生的。此外，E1A（13S）表达诱导两种形式的E4F-1的磷酸化，但差异调节其DNA结合活性，刺激了50 kDa的片段，同时降低了全长蛋白的活性。在瞬时转染测定中，在存在E1A（13S）的情况下，E4F-1氨基末端片段刺激了腺病毒E4启动子，而在没有但没有E1A的情况下，全长蛋白抑制了该启动子。结果表明，负责E4F DNA结合活性的50 kDa多肽是从phiAP3的人类同源物中产生的片段，并且两种形式的E4F-1蛋白受E1A通过磷酸化的调控。

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