Stephens Samuel B, Dodd Rebecca D, Lerner Rachel S, Pyhtila Brook M, Nicchitta Christopher V
Department of Cell Biology, Duke University Medical Center, Durham, NC, USA.
Methods Mol Biol. 2008;419:197-214. doi: 10.1007/978-1-59745-033-1_14.
All eukaryotic cells display a dramatic partitioning of mRNAs between the cytosol and endoplasmic reticulum (ER) compartments-mRNAs encoding secretory and integral membrane proteins are highly enriched on ER-bound ribosomes and mRNAs encoding cytoplasmic/nucleoplasmic proteins are enriched on cytosolic ribosomes. In current views, this partitioning phenomenon occurs through positive selection-mRNAs encoding signal sequence-bearing proteins are directed into the signal recognition particle pathway early in translation and trafficked as mRNA/ribosome/nascent polypeptide chain complexes to the ER. In the absence of an encoded signal sequence, mRNAs undergo continued translation on cytosolic ribosomes. Recent genome-wide analyses of mRNA partitioning between the cytosol and the ER compartments have identified subsets of mRNAs that are non-canonically partitioned to the ER-although lacking an encoded signal sequence, they are translated on ER-bound ribosomes. These findings suggest that multiple, and as yet unidentified, pathways exist for directing mRNA partitioning in the cell. In this contribution, we briefly review the literature describing the subcellular partitioning patterns of mRNAs and present a detailed methodology for studying this fundamental, yet poorly understood process.
所有真核细胞的mRNA在细胞质和内质网（ER）区室之间都呈现出显著的分隔现象——编码分泌蛋白和整合膜蛋白的mRNA在与内质网结合的核糖体上高度富集，而编码细胞质/核质蛋白的mRNA则在内质网核糖体上富集。在当前观点中，这种分隔现象是通过正选择发生的——编码带有信号序列蛋白的mRNA在翻译早期被引导进入信号识别颗粒途径，并作为mRNA/核糖体/新生多肽链复合物被转运到内质网。在没有编码信号序列的情况下，mRNA在内质网核糖体上继续翻译。最近对细胞质和内质网区室之间mRNA分隔的全基因组分析已经确定了非典型地被分隔到内质网的mRNA子集——尽管缺乏编码信号序列，但它们在内质网结合的核糖体上翻译。这些发现表明，细胞中存在多种尚未确定的途径来指导mRNA的分隔。在本论文中，我们简要回顾了描述mRNA亚细胞分隔模式的文献，并提出了一种详细的方法来研究这一基本但尚未得到充分理解的过程。
