Cloning and characterization of mr-s, a novel SAM domain protein, predominantly expressed in retinal photoreceptor cells
Cloning and characterization of mr-s, a novel SAM domain protein, predominantly expressed in retinal photoreceptor cells
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DOI：
10.1186/1471-213x-6-15
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发表时间：
2006-03-16
影响因子：
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通讯作者：
Furukawa, T
中科院分区：
文献类型：
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作者：
Inoue, T;Terada, K;Furukawa, T
背景：无菌α基序（SAM）结构域长度约为70个残基，已被报道为常见的蛋白质-蛋白质相互作用模块。该结构域存在于许多蛋白质中，包括Polycomb group （PcG）蛋白和ETS家族转录因子。在这项工作中，我们报道了一种新的含SAM结构域蛋白的克隆和功能表征，该蛋白主要表达于视网膜光感受器和松果体中，被命名为小鼠mr-s（主要视网膜SAM结构域蛋白）。结果：从斑马鱼到人类，mr-s在进化上是保守的，在生物体中，光感受器的发育机制也是高度保守的。系统发育分析表明，mr-s的SAM结构域与小鼠多同源（ph）同源物Mph1/Rae28最密切相关，后者是一种参与染色质修饰的表观遗传分子。这些发现提供了mr-s可能在光感受器发育中通过调节基因表达发挥关键作用的可能性。mr-s在出生后3-6天（P3-6）光感受器中优先表达，此时光感受器处于末梢分化阶段，并在成年松果体中表达。mr-s的转录是由锥杆同源结构域蛋白Crx直接调控的。免疫沉淀分析表明，mr-s蛋白主要通过含SAM结构域和ph区自结合。当mr-s在HEK293T细胞中过表达时，mr-s蛋白主要定位于细胞核。此外，在荧光素酶检测中，我们发现融合到GAL4 dna结合域的mr-s蛋白具有转录抑制因子的功能。我们发现mr-s的抑制活性不是由于其SAM结构域的亲同性相互作用，而是由于c端区域。结论：我们发现了一个主要在视网膜感光细胞和松果体中表达的新基因mr-s。根据其表达模式和生化分析，我们预测mr-s可能在松果体的光感受器细胞和松果体细胞中起转录抑制作用。
Background: Sterile alpha motif (SAM) domains are similar to 70 residues long and have been reported as common protein-protein interaction modules. This domain is found in a large number of proteins, including Polycomb group (PcG) proteins and ETS family transcription factors. In this work, we report the cloning and functional characterization of a novel SAM domain-containing protein, which is predominantly expressed in retinal photoreceptors and the pineal gland and is designated mouse mr-s ( major retinal SAM domain protein).Results: mr-s is evolutionarily conserved from zebrafish through human, organisms through which the mechanism of photoreceptor development is also highly conserved. Phylogenetic analysis suggests that the SAM domain of mr-s is most closely related to a mouse polyhomeotic (ph) ortholog, Mph1/Rae28, which is known as an epigenetic molecule involved in chromatin modifications. These findings provide the possibility that mr-s may play a critical role by regulating gene expression in photoreceptor development. mr-s is preferentially expressed in the photoreceptors at postnatal day 3 - 6 (P3-6), when photoreceptors undergo terminal differentiation, and in the adult pineal gland. Transcription of mr-s is directly regulated by the cone-rod homeodomain protein Crx. Immunoprecipitation assay showed that the mr-s protein self-associates mainly through the SAM domain-containing region as well as ph. The mr-s protein localizes mainly in the nucleus, when mr-s is overexpressed in HEK293T cells. Moreover, in the luciferase assays, we found that mr-s protein fused to GAL4 DNA-binding domain functions as a transcriptional repressor. We revealed that the repression activity of mr-s is not due to a homophilic interaction through its SAM domain but to the C-terminal region.Conclusion: We identified a novel gene, mr-s, which is predominantly expressed in retinal photoreceptors and pineal gland. Based on its expression pattern and biochemical analysis, we predict that mr-s may function as a transcriptional repressor in photoreceptor cells and in pinealocytes of the pineal gland.