Combinatorial binding leads to diverse regulatory responses: Lmd is a tissue-specific modulator of Mef2 activity.
Combinatorial binding leads to diverse regulatory responses: Lmd is a tissue-specific modulator of Mef2 activity.
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DOI：
10.1371/journal.pgen.1001014
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发表时间：
2010-07-01
期刊：
影响因子：
4.5
通讯作者：
Furlong EE
中科院分区：
文献类型：
--
作者：
Cunha PM;Sandmann T;Gustafson EH;Ciglar L;Eichenlaub MP;Furlong EE
了解时间和空间表达的复杂模式是如何被调节的，是破译驱动发育的遗传程序的核心。基因表达是通过转录因子及其辅助因子聚集在增强子元件上导致确定的活性而启动的。因此，组合占用的特定星座通常被概念化为刚性绑定代码，从而产生时空表达的共同输出。在这里，我们使用果蝇肌生成网络中两个基本转录因子的调节输入来评估这一假设。肌细胞增强因子2 （Mef2）或锌指转录因子跛脚鸭（lmd）的突变导致成肌细胞融合中非常相似的缺陷，但这种共同表型的潜在分子机制尚不清楚。通过结合ChIP-on-chip分析和功能缺失突变体的表达谱，我们获得了在发育过程中这两个因素的调控输入的全局视图。大多数lmd结合增强子与Mef2共结合，代表了Mef2在这些发育阶段的转录输入的一个子集。对这两个因素的调控贡献的系统分析表明，尽管它们共同占有共享的增强因子，但它们的调控作用却不尽相同。这些结果表明Lmd是Mef2活性的组织特异性调节剂，同时作为转录激活因子和抑制因子，这对肌肉发生具有重要意义。更一般地说，本研究表明两个因素的调节输出具有相当大的灵活性，从而导致共同调节的加性、合作和抑制模式。虽然遗传学研究对于揭示基因之间的表型关系至关重要，但通常很难解开两个相互表型的基因的分子机制。在这项研究中，我们使用全球规模和单基因分析来研究两种转录因子之间的关系，这两种转录因子的突变胚胎在肌肉发生中具有相似的缺陷。在果蝇中，Mef2突变胚胎在成肌细胞融合中表现出阻滞，这与在lmd（一种锌指转录因子）突变胚胎中观察到的情况非常相似。为了了解这些缺陷的潜在本质，我们使用ChIP-on-chip分析来获得它们的共调控增强子的全局视图，并使用突变胚胎的表达谱来揭示它们的下游转录反应。结果表明，Lmd是Mef2活性的组织特异性调节剂。通过体内和体外报告基因分析，我们发现与同一增强子元件的共结合可以导致不同的调控反应。Lmd的存在对Mef2活性具有附加、协同或抑制作用，表明它在肌肉分化过程中作为基因表达的分子开关。更广泛地说，我们的结果强调了将组合结合数据信息转化为功能调控响应的困难。
Understanding how complex patterns of temporal and spatial expression are regulated is central to deciphering genetic programs that drive development. Gene expression is initiated through the action of transcription factors and their cofactors converging on enhancer elements leading to a defined activity. Specific constellations of combinatorial occupancy are therefore often conceptualized as rigid binding codes that give rise to a common output of spatio-temporal expression. Here, we assessed this assumption using the regulatory input of two essential transcription factors within the Drosophila myogenic network. Mutations in either Myocyte enhancing factor 2 (Mef2) or the zinc-finger transcription factor lame duck (lmd) lead to very similar defects in myoblast fusion, yet the underlying molecular mechanism for this shared phenotype is not understood. Using a combination of ChIP-on-chip analysis and expression profiling of loss-of-function mutants, we obtained a global view of the regulatory input of both factors during development. The majority of Lmd-bound enhancers are co-bound by Mef2, representing a subset of Mef2's transcriptional input during these stages of development. Systematic analyses of the regulatory contribution of both factors demonstrate diverse regulatory roles, despite their co-occupancy of shared enhancer elements. These results indicate that Lmd is a tissue-specific modulator of Mef2 activity, acting as both a transcriptional activator and repressor, which has important implications for myogenesis. More generally, this study demonstrates considerable flexibility in the regulatory output of two factors, leading to additive, cooperative, and repressive modes of co-regulation. While genetic studies are essential to reveal the phenotypic relationships between genes, it is often very difficult to disentangle the molecular mechanism of two genes that phenocopy each other. In this study, we used global scale and single gene analysis to investigate the relationship between two transcription factors whose mutant embryos have a similar defect in myogenesis. In Drosophila, Mef2 mutant embryos display a block in myoblast fusion, which is very similar to what is observed in mutant embryos for lmd, a zinc-finger transcription factor. To understand the underlying nature of these defects we used ChIP-on-chip analysis to obtain a global view of their co-regulated enhancers, and we used expression profiling of mutant embryos to reveal their downstream transcriptional response. The results indicate that Lmd acts as a tissue specific modulator of Mef2 activity. Using in vivo and in vitro reporter assays, we show that co-binding to the same enhancer element can lead to diverse regulatory responses. The presence of Lmd has an additive, cooperative, or repressive effect on Mef2 activity, demonstrating that it acts as a molecular switch for gene expression during muscle differentiation. More broadly, our results highlight the difficulty in translating information on combinatorial binding data into a functional regulatory response.
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影响因子：
56.9
作者：
Furlong, EEM;Andersen, EC;Scott, MP
通讯作者：
Scott, MP
影响因子：
10.5
作者：
Penn, BH;Bergstrom, DA;Tapscott, SJ
通讯作者：
Tapscott, SJ
DOI：
10.1098/rstb.1995.0111
发表时间：
1995-09-29
期刊：
PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY OF LONDON SERIES B-BIOLOGICAL SCIENCES
影响因子：
--
作者：
GRAY, S;CAI, H;LEVINE, M
通讯作者：
LEVINE, M
影响因子：
10.5
作者：
Gray, S;Levine, M
通讯作者：
Levine, M
影响因子：
2.6
作者：
Kelly, KK;Meadows, SM;Cripps, RM
通讯作者：
Cripps, RM