Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA.
Proc Natl Acad Sci U S A. 2011 Nov 1;108(44):17985-90. doi: 10.1073/pnas.1113076108. Epub 2011 Oct 18.
A great deal is known about the export of spliced mRNAs, but little is known about the export of mRNAs encoded by human cellular genes that naturally lack introns. Here, we investigated the requirements for export of three naturally intronless mRNAs (HSPB3, IFN-α1, and IFN-β1). Significantly, we found that all three mRNAs are stable and accumulate in the cytoplasm, whereas size-matched random RNAs are unstable and detected only in the nucleus. A portion of the coding region confers this stability and cytoplasmic localization on the naturally intronless mRNAs and a cDNA transcript, which is normally retained in the nucleus and degraded. A polyadenylation signal, TREX mRNA export components, and the mRNA export receptor TAP are required for accumulation of the naturally intronless mRNAs in the cytoplasm. We conclude that naturally intronless mRNAs contain specific sequences that result in efficient packaging into the TREX mRNA export complex, thereby supplanting the splicing requirement for efficient mRNA export.
关于拼接 mRNA 的输出，人们已经了解很多，但对于天然缺乏内含子的人类细胞基因编码的 mRNA 的输出，人们知之甚少。在这里，我们研究了三种天然无内含子的 mRNA（HSPB3、IFN-α1 和 IFN-β1）的输出要求。重要的是，我们发现这三种 mRNA 都是稳定的，并在细胞质中积累，而大小匹配的随机 RNA 是不稳定的，只能在核内检测到。编码区的一部分赋予了这些天然无内含子的 mRNA 和 cDNA 转录本稳定性和细胞质定位，而 cDNA 转录本通常保留在核内并被降解。多聚腺苷酸化信号、 TREX mRNA 输出成分和 mRNA 输出受体 TAP 是将天然无内含子的 mRNA 在细胞质中积累所必需的。我们得出结论，天然无内含子的 mRNA 含有特定的序列，这些序列导致其有效地包装到 TREX mRNA 输出复合物中，从而取代了高效 mRNA 输出所需的拼接要求。
