Laboratory of Biochemistry, School of Life Sciences and Biotechnology, and BioInstitute, Korea University, Seoul, South Korea.
J Cell Biochem. 2010 May 15;110(2):294-303. doi: 10.1002/jcb.22537.
Ribosomal protein S3 (RpS3) is a well-known multi-functional protein mainly involved in protein biosynthesis as a member of the small ribosomal subunit. It also plays a role in repairing various DNA damage acting as a repair UV endonuclease. Most of the rpS3 pool is located in the ribosome while the minority exists in free form in the cytoplasm. We here report an additional function of rpS3 in which it represses its own translation by binding to its cognate mRNA. Through RT-PCR of the RNAs co-immunoprecipitated with ectopically expressed rpS3, rpS3 protein was found to interact with various RNAs-endogenous rpS3, 18S rRNA. The S3-C terminal domain was shown to be the major mRNA binding domain of rpS3, independent of the KH domain. This interaction was shown to occur in cytoplasmic fractions rather than ribosomal fractions, and then is involved in its own mRNA translational inhibition by in vitro translation. Furthermore, when Flag-tagged rpS3 was transiently transfected into 293T cells, the level of endogenous rpS3 gradually decreased regardless of transcription. These results suggest that free rpS3 regulates its own translation via a feedback mechanism.
核糖体蛋白 S3（RpS3）是一种众所周知的多功能蛋白，作为小核糖体亚基的一员，主要参与蛋白质生物合成。它还作为修复 UV 内切核酸酶在各种 DNA 损伤修复中发挥作用。大多数 RpS3 池位于核糖体中，而少数以游离形式存在于细胞质中。我们在这里报告了 RpS3 的另一个功能，即通过与自身同源的 mRNA 结合来抑制自身翻译。通过与异位表达的 RpS3 共免疫沉淀的 RNA 的 RT-PCR，发现 RpS3 蛋白与各种 RNA（内源性 RpS3、18S rRNA）相互作用。S3-C 末端结构域被证明是 RpS3 的主要 mRNA 结合结构域，不依赖于 KH 结构域。这种相互作用发生在细胞质部分而不是核糖体部分，然后通过体外翻译参与其自身 mRNA 的翻译抑制。此外，当 Flag 标记的 RpS3 瞬时转染到 293T 细胞中时，无论转录如何，内源性 RpS3 的水平逐渐降低。这些结果表明，游离的 RpS3 通过反馈机制调节自身的翻译。
