Department of Biology, Emory University, Atlanta, GA, USA.
Cell Cycle. 2013 May 15;12(10):1605-15. doi: 10.4161/cc.24742. Epub 2013 Apr 25.
DREF was first characterized for its role in the regulation of transcription of genes encoding proteins involved in DNA replication and found to interact with sequences similar to the DNA recognition motif of the BEAF-32 insulator protein. Insulators are DNA-protein complexes that mediate intra- and inter-chromosome interactions. Several DNA-binding insulator proteins have been described in Drosophila, including BEAF-32, dCTCF and Su(Hw). Here we find that DREF and BEAF-32 co-localize at the same genomic sites, but their enrichment shows an inverse correlation. Furthermore, DREF co-localizes in the genome with other insulator proteins, suggesting that the function of this protein may require components of Drosophila insulators. This is supported by the finding that mutations in insulator proteins modulate DREF-induced cell proliferation. DREF persists bound to chromatin during mitosis at a subset of sites where it also co-localizes with dCTCF, BEAF-32 and CP190. These sites are highly enriched for sites where Orc2 and Mcm2 are present during interphase and at the borders of topological domains of chromosomes defined by Hi-C. The results suggest that DREF and insulator proteins may help maintain chromosome organization during the cell cycle and mark a subset of genomic sites for the assembly of pre-replication complexes and gene bookmarking during the M/G1 transition.
DREF 最初因其在调节编码参与 DNA 复制的蛋白质的基因转录中的作用而被描述，并发现与 BEAF-32 绝缘子蛋白的 DNA 识别基序相似的序列相互作用。绝缘子是介导染色体内和染色体间相互作用的 DNA-蛋白质复合物。在果蝇中已经描述了几种 DNA 结合绝缘子蛋白，包括 BEAF-32、dCTCF 和 Su(Hw)。在这里，我们发现 DREF 和 BEAF-32 共定位在相同的基因组位点，但它们的富集呈负相关。此外，DREF 在基因组中与其他绝缘子蛋白共定位，表明该蛋白的功能可能需要果蝇绝缘子的成分。这一发现得到了支持，即绝缘子蛋白的突变会调节 DREF 诱导的细胞增殖。DREF 在有丝分裂期间持续结合到染色质上，在其中一些与 dCTCF、BEAF-32 和 CP190 共定位的位点上也是如此。这些位点高度富集了 Orc2 和 Mcm2 在有丝分裂间期存在的位点，以及由 Hi-C 定义的染色体拓扑结构域的边界。结果表明，DREF 和绝缘子蛋白可能有助于在细胞周期中维持染色体组织，并在 M/G1 转换期间为预复制复合物的组装和基因标记选择基因组的一部分。
