Han J R, Yiu G K, Hecht N B
Department of Biology, Tufts University, Medford, MA 02155, USA.
Proc Natl Acad Sci U S A. 1995 Oct 10;92(21):9550-4. doi: 10.1073/pnas.92.21.9550.
We have previously identified a testicular phosphoprotein that binds to highly conserved sequences (Y and H elements) in the 3' untranslated regions (UTRs) of testicular mRNAs and suppresses in vitro translation of mRNA constructs that contain these sequences. This protein, testis/brain RNA-binding protein (TB-RBP) also is abundant in brain and binds to brain mRNAs whose 3' UTRs contain similar sequences. Here we show that TB-RBP binds specific mRNAs to microtubules (MTs) in vitro. When TB-RBP is added to MTs reassembled from either crude brain extracts or from purified tubulin, most of the TB-RBP binds to MTs. The association of TB-RBP with MTs requires the assembly of MTs and is diminished by colcemid, cytochalasin D, and high levels of salt. Transcripts from the 3' UTRs of three mRNAs that contain the conserved sequence elements (transcripts for protamine 2, tau protein, and myelin basic protein) are linked by TB-RBP to MTs, whereas transcripts that lack the conserved sequences do not bind TB-RBP. We conclude that TB-RBP serves as an attachment protein for the MT association of specific mRNAs. Considering its ability to arrest translation in vitro, we propose that TB-RBP functions in the storage and transportation of mRNAs to specific intracellular sites where they are translated.
我们之前鉴定出一种睾丸磷蛋白，它能与睾丸mRNA的3'非翻译区（UTR）中的高度保守序列（Y和H元件）结合，并抑制包含这些序列的mRNA构建体的体外翻译。这种蛋白，即睾丸/脑RNA结合蛋白（TB-RBP），在脑中也很丰富，并与3'UTR包含相似序列的脑mRNA结合。在此我们表明，TB-RBP在体外能将特定mRNA与微管（MT）结合。当将TB-RBP添加到从粗脑提取物或纯化微管蛋白重新组装的微管中时，大部分TB-RBP会与微管结合。TB-RBP与微管的结合需要微管的组装，并且会被秋水仙酰胺、细胞松弛素D和高浓度盐减弱。三种含有保守序列元件的mRNA的3'UTR转录本（鱼精蛋白2、tau蛋白和髓鞘碱性蛋白的转录本）通过TB-RBP与微管相连，而缺乏保守序列的转录本则不与TB-RBP结合。我们得出结论，TB-RBP作为特定mRNA与微管结合的附着蛋白。考虑到其在体外阻止翻译的能力，我们提出TB-RBP在mRNA的储存和运输至特定细胞内翻译位点的过程中发挥作用。
