Drosophila SUMM4 complex couples insulator function and DNA replication control.
Drosophila SUMM4 complex couples insulator function and DNA replication control.
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DOI：
10.7554/elife.81828
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发表时间：
2022-12-02
期刊：
影响因子：
7.7
通讯作者：
Fyodorov DV
中科院分区：
文献类型：
--
作者：
Andreyeva EN;Emelyanov AV;Nevil M;Sun L;Vershilova E;Hill CA;Keogh MC;Duronio RJ;Skoultchi AI;Fyodorov DV
S 期染色体结构域的异步复制对于真核基因组功能至关重要，但确定哪些结构域在不同细胞类型中早期复制和晚期复制的机制仍不完全清楚。居间异染色质结构域在分裂细胞的二倍体染色体和内复制多线染色体中复制得很晚，它们的复制也不足。果蝇 SNF2 相关因子 SUUR 导致多线染色体的位点特异性复制不足。 SUUR 负向调节 DNA 复制叉进展；然而，其作用机制仍不清楚。在这里，我们开发了一种称为 MS 启用的快速蛋白质复合物鉴定 (MERCI) 的新方法，用于分离包含 SUUR 和染色质边界蛋白 Mod(Mdg4)-67.2 的稳定化学计量天然复合物 SUMM4。 Mod(Mdg4) 刺激 SUUR ATP 酶活性，是 SUUR 体内正常时空分布所必需的。 SUUR 和 Mod(Mdg4)-67.2 共同介导吉普赛绝缘子的活性，防止某些增强子-启动子相互作用，并在基因组中建立常染色质-异染色质屏障。此外，SuUR 或 mod(mdg4) 突变可逆转居间异染色质的复制不足。因此，SUMM4 可以通过减弱复制叉穿过常染色质/异染色质边界的进展来赋予居间异染色质的晚期复制。我们的研究结果表明 SNF2 家族 ATP 依赖性运动蛋白 SUUR 参与了绝缘子功能，揭示了 DNA 复制可以被染色质屏障延迟，并揭示了结构蛋白在复制控制中的关键作用。他们提出了一种建立后期复制的机制，该机制不依赖于后期复制源的异步触发。在细胞内，DNA 分子提供制造蛋白质所需的指令。细胞小心地维护和修复它们的DNA，并且通常在分裂之前制作完整的基因组副本，以确保分裂后，每个子细胞都有完整的基因组。在人类、果蝇和其他真核生物的细胞核内，DNA 被包装成称为染色体的结构。细胞遵循精确控制的程序在不同时间复制染色体的不同区域。为了开始复制特定区域，复制 DNA 的细胞机器会与称为复制起点的序列结合。据认为，来自细胞的未知线索可能导致复制机制在不同时间与不同的复制起点结合。在某些情况下，细胞会在不分裂的情况下产生额外的 DNA 副本。例如，果蝇幼虫中的许多细胞含有数百个额外的 DNA 拷贝，以维持其增大的体型。然而，在此过程中整个基因组并未被复制，因此细胞最终会比其他区域获得更多基因组某些区域的副本。阻碍“代表性不足”区域的复制需要一种名为 SUUR 的蛋白质，但尚不清楚它是如何发挥作用的。为了解决这个问题，Andreyeva、Emelyanov 等人。开发了一种基于液相色谱和定量蛋白质组学的新方法来鉴定果蝇中 SUUR 的天然形式。这表明 SUUR 与一种名为 Mod(Mdg4) 的蛋白质形成稳定的复合物，而 Mod(Mdg4) 是将 SUUR 招募到染色体上所必需的。进一步的实验表明，SUUR 和 Mod(Mdg4) 共同作用，与称为吉普赛绝缘体元件的 DNA 区域结合，形成物理屏障，阻碍复制机制访问基因组的某些部分。 Andreyeva、Emelyanov 等人的研究结果。为单个细胞如何错开复制其 DNA 的过程提供了另一种解释，而不依赖于在不同时间与不同复制起点结合的复制机制。相反，晚期复制时间可能是由特定基因组区域上复制进程的绝缘体产生的延迟来指示的。这种机制增加了已知由绝缘子和相关结构蛋白指导的核过程（染色体分配、转录调节等）的列表。
Asynchronous replication of chromosome domains during S phase is essential for eukaryotic genome function, but the mechanisms establishing which domains replicate early versus late in different cell types remain incompletely understood. Intercalary heterochromatin domains replicate very late in both diploid chromosomes of dividing cells and in endoreplicating polytene chromosomes where they are also underreplicated. Drosophila SNF2-related factor SUUR imparts locus-specific underreplication of polytene chromosomes. SUUR negatively regulates DNA replication fork progression; however, its mechanism of action remains obscure. Here, we developed a novel method termed MS-Enabled Rapid protein Complex Identification (MERCI) to isolate a stable stoichiometric native complex SUMM4 that comprises SUUR and a chromatin boundary protein Mod(Mdg4)-67.2. Mod(Mdg4) stimulates SUUR ATPase activity and is required for a normal spatiotemporal distribution of SUUR in vivo. SUUR and Mod(Mdg4)-67.2 together mediate the activities of gypsy insulator that prevent certain enhancer–promoter interactions and establish euchromatin–heterochromatin barriers in the genome. Furthermore, SuUR or mod(mdg4) mutations reverse underreplication of intercalary heterochromatin. Thus, SUMM4 can impart late replication of intercalary heterochromatin by attenuating the progression of replication forks through euchromatin/heterochromatin boundaries. Our findings implicate a SNF2 family ATP-dependent motor protein SUUR in the insulator function, reveal that DNA replication can be delayed by a chromatin barrier, and uncover a critical role for architectural proteins in replication control. They suggest a mechanism for the establishment of late replication that does not depend on an asynchronous firing of late replication origins. Inside cells, molecules of DNA provide the instructions needed to make proteins. Cells carefully maintain and repair their DNA, and typically make a complete copy of the genome before they divide to ensure that after division, each daughter cell has a full set. Within human, fly and other eukaryotic nuclei, DNA is packaged into structures known as chromosomes. Cells follow precisely controlled programs to replicate distinct regions of chromosomes at different times. To start copying a particular region, the cell machinery that replicates DNA binds to a sequence known as the origin of replication. It is thought that as-yet unknown cues from the cell may lead the replication machinery to bind to different origins of replication at different times. In some circumstances, cells make extra copies of their DNA without dividing. For example, many cells in the larvae of fruit flies contain hundreds of extra DNA copies to sustain their increased sizes. However, the entire genome is not copied during this process, so cells end up with more copies of some regions of the genome than others. A protein called SUUR is required for hindering the replication of the ‘underrepresented’ regions, but it is not clear how it works. To address this question, Andreyeva, Emelyanov et al. developed a new approach based on liquid chromatography and quantitative proteomics to identify the native form of SUUR in fruit flies. This revealed that SUUR exists as a stable complex with a protein called Mod(Mdg4), which is needed to recruit SUUR to the chromosomes. Further experiments suggested that SUUR and Mod(Mdg4) work together to bind to regions of DNA known as gypsy insulator elements, creating a physical barrier that hinders the replication machinery from accessing some parts of the genome. The findings of Andreyeva, Emelyanov et al. provide an alternative explanation for how individual cells may stagger the process of copying their DNA without relying on the replication machinery binding to various replication origins at different times. Rather, late replication timing may be instructed by an insulator-born delay of the progression of replication over particular genomic regions. This mechanism adds to the list of nuclear processes (chromosome partitioning, transcriptional regulation, etc.) that are known to be directed by insulators and associated architectural proteins.
影响因子：
12.3
作者：
Adryan B;Woerfel G;Birch-Machin I;Gao S;Quick M;Meadows L;Russell S;White R
通讯作者：
White R