Cancer Research UK, Cambridge Research Institute, Li Ka Shing Centre, Cambridge CB2 0RE, United Kingdom.
Genome Res. 2010 May;20(5):578-88. doi: 10.1101/gr.100479.109. Epub 2010 Mar 10.
The cohesin protein complex holds sister chromatids in dividing cells together and is essential for chromosome segregation. Recently, cohesin has been implicated in mediating transcriptional insulation, via its interactions with CTCF. Here, we show in different cell types that cohesin functionally behaves as a tissue-specific transcriptional regulator, independent of CTCF binding. By performing matched genome-wide binding assays (ChIP-seq) in human breast cancer cells (MCF-7), we discovered thousands of genomic sites that share cohesin and estrogen receptor alpha (ER) yet lack CTCF binding. By use of human hepatocellular carcinoma cells (HepG2), we found that liver-specific transcription factors colocalize with cohesin independently of CTCF at liver-specific targets that are distinct from those found in breast cancer cells. Furthermore, estrogen-regulated genes are preferentially bound by both ER and cohesin, and functionally, the silencing of cohesin caused aberrant re-entry of breast cancer cells into cell cycle after hormone treatment. We combined chromosomal interaction data in MCF-7 cells with our cohesin binding data to show that cohesin is highly enriched at ER-bound regions that capture inter-chromosomal loop anchors. Together, our data show that cohesin cobinds across the genome with transcription factors independently of CTCF, plays a functional role in estrogen-regulated transcription, and may help to mediate tissue-specific transcriptional responses via long-range chromosomal interactions.
黏连蛋白复合物将分裂细胞中的姐妹染色单体保持在一起，对于染色体分离至关重要。最近，黏连蛋白通过与 CTCF 的相互作用，被牵连到介导转录隔离中。在这里，我们在不同的细胞类型中表明，黏连蛋白作为一种组织特异性转录调节剂发挥功能，而不依赖于 CTCF 结合。通过在人乳腺癌细胞（MCF-7）中进行匹配的全基因组结合测定（ChIP-seq），我们发现了数千个基因组位点，这些位点共享黏连蛋白和雌激素受体 alpha（ER），但缺乏 CTCF 结合。通过使用人肝癌细胞（HepG2），我们发现肝特异性转录因子与黏连蛋白独立于 CTCF 共定位在肝特异性靶标上，这些靶标与在乳腺癌细胞中发现的靶标不同。此外，雌激素调节的基因优先被 ER 和黏连蛋白结合，并且功能上，在激素处理后，黏连蛋白的沉默导致乳腺癌细胞异常重新进入细胞周期。我们将 MCF-7 细胞中的染色体相互作用数据与我们的黏连蛋白结合数据结合起来，表明黏连蛋白在捕获染色体间环锚定的 ER 结合区域高度富集。总之，我们的数据表明，黏连蛋白在全基因组上与转录因子独立于 CTCF 共同结合，在雌激素调节的转录中发挥功能作用，并可能通过长距离染色体相互作用帮助介导组织特异性转录反应。
