Transcription factor MITF and remodeller BRG1 define chromatin organisation at regulatory elements in melanoma cells.
Transcription factor MITF and remodeller BRG1 define chromatin organisation at regulatory elements in melanoma cells.
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DOI：
10.7554/elife.06857
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发表时间：
2015-03-24
期刊：
影响因子：
7.7
通讯作者：
Davidson I
中科院分区：
文献类型：
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作者：
Laurette P;Strub T;Koludrovic D;Keime C;Le Gras S;Seberg H;Van Otterloo E;Imrichova H;Siddaway R;Aerts S;Cornell RA;Mengus G;Davidson I
小眼相关转录因子（MITF）是黑素细胞谱系的主要调节因子。为了了解MITF如何调节转录，我们使用串联亲和纯化和质谱技术定义了一个全面的MITF相互作用组，鉴定了参与转录、DNA复制和修复以及染色质组织的新辅助因子。我们发现MITF与包含BRG1和CHD7的PBAF染色质重塑复合体相互作用。BRG1是体外黑色素瘤细胞增殖和体内正常黑色素细胞发育所必需的。MITF和SOX10积极地将BRG1招募到活跃增强子上的MITF相关调控元件（MAREs）。MITF、SOX10、TFAP2A和YY1的组合结合在两个brg1占据的核小体之间，从而定义了黑素细胞谱系所必需的转录因子的特征和它们占据的调节元件的特定染色质组织。BRG1还调节MITF基因组占用的动态。因此，MITF-BRG1相互作用在黑色素瘤的转录调控中起着至关重要的作用。DOI: http://dx.doi.org/10.7554/eLife.06857.001黑色素细胞是主要在皮肤中发现的色素生成细胞。许多帮助这些细胞发育的基因也被认为会影响黑色素瘤的发展：黑色素瘤是一种起源于这些细胞的侵袭性皮肤癌。其中一个基因编码一种叫做MITF的蛋白质。这种蛋白质与DNA结合，并调节控制黑素细胞发育、存活和扩散的基因；它还与黑色素瘤的侵袭性有关。MITF蛋白与伴侣蛋白一起控制许多基因，通过与充当调控元件的附近DNA片段结合，激活一些基因，抑制另一些基因。因此，它的相互作用是广泛而复杂的。现在，Laurette， Strub等人已经使用串联亲和纯化和质谱技术来鉴定与MITF相互作用的蛋白质。这项研究发现了许多新的MITF蛋白伙伴，包括参与DNA损伤、修复和复制的蛋白质。MITF还与两种蛋白质相关联，其中一种叫做brg1，它们参与改变DNA在细胞内包装的紧密程度。包裹在蛋白质周围的DNA被称为染色质，如果染色质被紧密包裹，那么这段DNA中的基因就不容易被接触或激活。从黑色素细胞和黑色素瘤细胞中去除BRG1会导致细胞死亡或停止生长。当BRG1从发育中的小鼠胚胎中移除时，黑素细胞无法形成。进一步的研究表明，MITF与另一种蛋白质一起，将BRG1定位到黑素细胞DNA的位置，打开染色质并调节附近的基因。此外，Laurette、Strub等人报道，BRG1以一种特有的方式与许多此类元件结合，其中两个BRG1蛋白位于MITF和其他几个关键DNA结合蛋白结合的DNA片段的侧面，这些DNA结合蛋白共同调节黑素细胞和黑色素瘤细胞生理学的许多方面。因此，Laurette， Strub等人揭示了激活黑素瘤和黑素细胞中基因的分子的许多细节，以及这些分子之间的相互作用。研究结果还可以帮助研究人员了解BRG1蛋白如何在其他细胞类型中组织染色质堆积。DOI: http://dx.doi.org/10.7554/eLife.06857.002
Microphthalmia-associated transcription factor (MITF) is the master regulator of the melanocyte lineage. To understand how MITF regulates transcription, we used tandem affinity purification and mass spectrometry to define a comprehensive MITF interactome identifying novel cofactors involved in transcription, DNA replication and repair, and chromatin organisation. We show that MITF interacts with a PBAF chromatin remodelling complex comprising BRG1 and CHD7. BRG1 is essential for melanoma cell proliferation in vitro and for normal melanocyte development in vivo. MITF and SOX10 actively recruit BRG1 to a set of MITF-associated regulatory elements (MAREs) at active enhancers. Combinations of MITF, SOX10, TFAP2A, and YY1 bind between two BRG1-occupied nucleosomes thus defining both a signature of transcription factors essential for the melanocyte lineage and a specific chromatin organisation of the regulatory elements they occupy. BRG1 also regulates the dynamics of MITF genomic occupancy. MITF-BRG1 interplay thus plays an essential role in transcription regulation in melanoma. DOI: http://dx.doi.org/10.7554/eLife.06857.001 Melanocytes are pigment-producing cells found primarily in the skin. Many of the genes that help these cells to develop are also thought to affect the development of melanomas: an aggressive form of skin cancer that originates in these cells. One such gene encodes a protein called MITF. This protein binds to DNA and regulates genes that control the development, survival, and spread of melanocytes; it is also linked to the invasive properties of melanomas. The MITF protein works together with partner proteins to control numerous genes, activating some while inhibiting others, by binding to nearby stretches of DNA that act as regulatory elements. Its interactions are therefore widespread and complex. Now, Laurette, Strub et al. have used techniques called tandem affinity purification and mass spectrometry to identify the proteins that interact with MITF. This investigation found many new protein partners for MITF, including proteins involved in DNA damage, repair, and replication. MITF also associates with two proteins—one of which is called BRG1—that are involved in modifying how tightly DNA is packaged inside cells. DNA wrapped around proteins is known as chromatin, and if chromatin is tightly packed, the genes in that stretch of DNA cannot be easily accessed or activated. Removing BRG1 from melanocytes and melanoma cells caused the cells to die or stop growing. When BRG1 was removed from developing mouse embryos, melanocytes failed to form. Further investigation revealed that MITF, together with another protein, localize BRG1 to sites in the melanocyte's DNA to open up the chromatin and regulate nearby genes. Furthermore, Laurette, Strub et al. report that BRG1 binds to many such elements in a characteristic manner, in which two BRG1 proteins flank the stretch of DNA bound by MITF and several other key DNA-binding proteins that together regulate many aspects of melanocyte and melanoma cell physiology. Laurette, Strub et al. have therefore revealed many details about the molecules that activate genes in melanomas and melanocyte cells, as well as the interactions between these molecules. The results could also help researchers to understand how the BRG1 protein organises chromatin packing in other cell types. DOI: http://dx.doi.org/10.7554/eLife.06857.002