Selective genomic targeting by FRA-2/FOSL2 transcription factor: regulation of the Rgs4 gene is mediated by a variant activator protein 1 (AP-1) promoter sequence/CREB-binding protein (CBP) mechanism.
Selective genomic targeting by FRA-2/FOSL2 transcription factor: regulation of the Rgs4 gene is mediated by a variant activator protein 1 (AP-1) promoter sequence/CREB-binding protein (CBP) mechanism.
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DOI：
10.1074/jbc.m110.201996
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发表时间：
2011-04-29
期刊：
影响因子：
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通讯作者：
Carter DA
中科院分区：
文献类型：
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作者：
Davies JS;Klein DC;Carter DA
FRA-2/FOSL2是一个基本的区域亮氨酸拉链基序转录因子，在哺乳动物组织中广泛表达。该因子的功能谱系尚不清楚，部分原因是缺乏对靶向基因组序列的了解。在这里，我们通过基因敲除转基因大鼠的表达谱分析，确定了整个基因组中新的、有功能的FRA-2靶点。在这个模型中，松果体FRA-2的夜间节律被一种遗传编码的显性负性突变蛋白抑制。对FRA-2调控和非调控基因的生物信息学分析表明，FRA-2调节子受到基因组靶标选择规则的限制，这些规则通常超越核心顺式序列同一性。然而，一个变异的AP-1相关(AP-1R)序列是调控基因的一个子集所共有的。对一个新的FRA-2抑制基因RGS4的候选AP-1R序列的功能活性和蛋白结合伙伴进行了测定。体外芯片和体外EMSA分析表明，FRA-2蛋白优先与RGS4 AP-1R近端序列相关；此外，AP-1R序列的突变阻止了转录抑制，而上游共识AP-1家族序列的突变不影响RGS4的表达。RGS4 AP-1R序列蛋白质复合体的夜间变化与FRA-2依赖的共激活因子CBP的消除有关，这为RGS4基因抑制提供了机制基础。这些研究还为FRA-2选择性基因组靶向提供了功能洞察力，突出了预测靶点和实际靶点之间的不一致。未来的研究应该解决FRA-2和RGS4在其他系统中的相互作用，包括大脑，因为FRA-2的功能在大脑中知之甚少。
FRA-2/FOSL2 is a basic region-leucine zipper motif transcription factor that is widely expressed in mammalian tissues. The functional repertoire of this factor is unclear, partly due to a lack of knowledge of genomic sequences that are targeted. Here, we identified novel, functional FRA-2 targets across the genome through expression profile analysis in a knockdown transgenic rat. In this model, a nocturnal rhythm of pineal gland FRA-2 is suppressed by a genetically encoded, dominant negative mutant protein. Bioinformatic analysis of validated sets of FRA-2-regulated and -nonregulated genes revealed that the FRA-2 regulon is limited by genomic target selection rules that, in general, transcend core cis-sequence identity. However, one variant AP-1-related (AP-1R) sequence was common to a subset of regulated genes. The functional activity and protein binding partners of a candidate AP-1R sequence were determined for a novel FRA-2-repressed gene, Rgs4. FRA-2 protein preferentially associated with a proximal Rgs4 AP-1R sequence as demonstrated by ex vivo ChIP and in vitro EMSA analysis; moreover, transcriptional repression was blocked by mutation of the AP-1R sequence, whereas mutation of an upstream consensus AP-1 family sequence did not affect Rgs4 expression. Nocturnal changes in protein complexes at the Rgs4 AP-1R sequence are associated with FRA-2-dependent dismissal of the co-activator, CBP; this provides a mechanistic basis for Rgs4 gene repression. These studies have also provided functional insight into selective genomic targeting by FRA-2, highlighting discordance between predicted and actual targets. Future studies should address FRA-2-Rgs4 interactions in other systems, including the brain, where FRA-2 function is poorly understood.