Yang Mary Qu, Elnitski Laura L
National Human Genome Research Institute, National Institutes Health, Rockville, MD 20852, USA.
BMC Genomics. 2008 Sep 16;9 Suppl 2(Suppl 2):S3. doi: 10.1186/1471-2164-9-S2-S3.
Bidirectional promoters lie between adjacent genes, which are transcribed from opposite strands of DNA. The functional mechanisms underlying the activation of bidirectional promoters are currently uncharacterised. To define the core promoter elements of bidirectional promoters in human, we mapped motifs for TATA, INR, BRE, DPE, INR, as well as CpG-islands.
We found a consistently high correspondence between C+G content, CpG-island presence and an average expression level increasing the median level for all genes in bidirectional promoters. These CpG-rich promoters showed discrete initiation patterns rather than broad regions of transcription initiation, as are typically seen for CpG-island promoters. CpG-islands encompass both TSSs within bidirectional promoters, providing an explanation for the symmetrical co-expression patterns of many of these genes. In contrast, TATA motifs appear to be asymmetrically positioned at one TSS or the other.
Our findings demonstrate that bidirectional promoters utilize a variety of core promoter elements to initiate transcription. CpG-islands dominate the regulatory landscape of this group of promoters.
双向启动子位于相邻基因之间，这些基因从DNA的相反链转录而来。目前，双向启动子激活的功能机制尚不明确。为了确定人类双向启动子的核心启动子元件，我们绘制了TATA、INR、BRE、DPE、INR以及CpG岛的基序图谱。
我们发现，双向启动子中所有基因的C+G含量、CpG岛的存在与平均表达水平升高的中位数水平之间始终存在高度相关性。这些富含CpG的启动子表现出离散的起始模式，而非CpG岛启动子常见的广泛转录起始区域。CpG岛包含双向启动子内的两个转录起始位点（TSS），这为许多此类基因的对称共表达模式提供了解释。相比之下，TATA基序似乎不对称地位于其中一个TSS处。
我们的研究结果表明，双向启动子利用多种核心启动子元件来启动转录。CpG岛在这组启动子的调控格局中占主导地位。
