Regulation of human papillomavirus type 31 gene expression during the differentiation-dependent life cycle through histone modifications and transcription factor binding.
Regulation of human papillomavirus type 31 gene expression during the differentiation-dependent life cycle through histone modifications and transcription factor binding.
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DOI：
10.1016/j.virol.2007.12.011
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发表时间：
2008-05
期刊：
影响因子：
3.7
通讯作者：
Tonia R Wooldridge;L. Laimins
中科院分区：
文献类型：
--
作者：
Tonia R Wooldridge;L. Laimins
高危型人乳头瘤病毒的生命周期与上皮细胞分化有关，病毒体的产生仅限于高度分化的基底上细胞。两种主要的病毒启动子指导高危型HPV基因表达，它们的活性取决于分化。早期启动子控制E6开放阅读框上游位点转录物的起始，在未分化和分化细胞中都有活性。晚期病毒启动子指导E7中一系列异质起始位点的转录，并在分化时被激活。在这项研究中，组蛋白的状态，以及在未分化和分化的细胞中的两个主要的HPV 31病毒启动子结合的转录因子的光谱进行了检查，使用染色质免疫沉淀试验。我们的研究表明，在未分化的细胞中，两个启动子区域周围的染色质是在一个开放的，转录活性状态所示的组蛋白H3 K4以及乙酰化H3和乙酰化H4的二甲基化形式的存在。分化后，在两个启动子区域周围二甲基化H3 K4和乙酰化H3的水平分别增加了4至6倍，并且在早期启动子处乙酰化H4增加了约9倍。这表明两个启动子区域的核小体在分化过程中通过组蛋白修饰被进一步激活。染色质免疫沉淀试验也被用来检查结合的角质形成细胞增强子（KE）/早期启动子区的上游调控区（URR）和晚期启动子序列在整个分化的转录因子。我们的研究结果表明，在两个区域的转录因子结合发生动态变化分化后，最显着的显着增加C/EBP-β结合KE/早期启动子区域以及C/EBP-α结合晚期启动子区域分化后。这些结合的增加不能仅仅通过分化后这些因子的总细胞水平的变化来解释，而是反映了对HPV基因组特异性结合的增加。最后，瞬时表达分析证实，KE/早期启动子区域的URR的贡献显着激活晚期基因表达，这是一致的，通过多种转录因子的组合结合的调节。
The life cycle of high-risk human papillomaviruses is linked to epithelial differentiation with virion production restricted to highly differentiated suprabasal cells. Two major viral promoters direct high-risk HPV gene expression and their activities are dependent upon differentiation. The early promoter controls initiation of transcripts at sites upstream of the E6 open reading frame and is active in both undifferentiated as well as differentiated cells. The late viral promoter directs transcription from a series of heterogeneous start sites in E7 and is activated upon differentiation. In this study, the state of histones as well as the spectrum of transcription factors bound to the two major HPV 31 viral promoters in undifferentiated and differentiated cells were examined using chromatin immunoprecipitation assays. Our studies indicate that, in undifferentiated cells, the chromatin surrounding both promoter regions is in an open, transcriptionally active state as indicated by the presence of dimethylated forms of histone H3 K4 as well as acetylated H3 and acetylated H4. Upon differentiation, there was an increase of four to six fold in the levels of dimethylated H3K4 and acetylated H3 respectively around both promoter regions as well as an increase of approximately nine fold in acetylated H4 at the early promoter. This suggests that nucleosomes of both promoter regions are further activated through histone modifications during differentiation. Chromatin immunoprecipitation assays were also used to examine the binding of transcription factors to the keratinocyte enhancer (KE)/early promoter region in the upstream regulatory region (URR) and late promoter sequences throughout differentiation. Our results suggest that a dynamic change in transcription factor binding occurs in both regions upon differentiation; most notably a significant increase in C/EBP-β binding to the KE/early promoter region as well as C/EBP-α binding to the late promoter region upon differentiation. These increases in binding cannot be solely explained by changes in the total cellular levels of these factors following differentiation, but instead reflect increased binding specific to HPV genomes. Finally, transient expression analyses confirmed that the KE/early promoter region of the URR contributes significantly to the activation of late gene expression and this is consistent with regulation through the combinatorial binding of multiple transcription factors.