Testis-brain RNA-binding protein (TB-RBP/Translin) is known to contribute to the translational repression of a subset of haploid cell-specific mRNAs, including protamine 2 (Prm2) mRNA. Mutant mice lacking TB-RBP display abnormal spermatogenesis, despite normal male fertility. In this study, we carried out functional analysis of TB-RBP in mammalian cultured cells to understand the mechanism of translational repression by this RNA-binding protein. Although the amino acid sequence contained a eukaryotic translation initiation factor 4E (EIF4E)-recognition motif, TB-RBP failed to interact with EIF4E. In cultured cells, TB-RBP was unable to reduce the activity of luciferase encoded by a reporter mRNA carrying the 3'-untranslated region of Prm2. However, λΝ-BoxB tethering assay revealed that the complex of TB-RBP with its binding partner, Translin-associated factor X (TRAX), exhibits the ability to reduce the luciferase reporter activity by degrading the mRNA. These results suggest that TB-RBP may play a regulatory role in determining the sequence specificity of TRAX-catalyzed mRNA degradation.

中文翻译：

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睾丸脑 RNA 结合蛋白的功能表征，TB-RBP/Translin，在翻译调节中

众所周知，睾丸脑 RNA 结合蛋白 (TB-RBP/Translin) 有助于抑制一部分单倍体细胞特异性 mRNA，包括鱼精蛋白 2 (Prm2) mRNA。尽管雄性生育力正常，但缺乏 TB-RBP 的突变小鼠表现出异常的精子发生。在这项研究中，我们对哺乳动物培养细胞中的 TB-RBP 进行了功能分析，以了解这种 RNA 结合蛋白的翻译抑制机制。尽管氨基酸序列包含真核翻译起始因子 4E (EIF4E) 识别基序，但 TB-RBP 未能与 EIF4E 相互作用。在培养的细胞中，TB-RBP 无法降低携带 Prm2 3'-非翻译区的报告基因 mRNA 编码的荧光素酶的活性。然而，λΝ-BoxB 系绳测定显示 TB-RBP 与其结合配偶体的复合物，Translin 相关因子 X (TRAX) 表现出通过降解 mRNA 来降低荧光素酶报告基因活性的能力。这些结果表明 TB-RBP 可能在确定 TRAX 催化的 mRNA 降解的序列特异性方面发挥调节作用。