Institut fuer Biochemie, OE4310, Medizinische Hochschule Hannover, Carl-Neuberg-Street 1, Hannover D-30623, Germany.
Cell Death Dis. 2013 Oct 24;4(10):e879. doi: 10.1038/cddis.2013.409.
Hematopoiesis and commitment to a restricted lineage are guided by a timely expressed set of cytokine receptors and their downstream transcription factors. A member of the mRNA export complex, THOC5 (suppressors of the transcriptional defects of hpr1 delta by overexpression complex 5) is a substrate for several tyrosine kinases such as macrophage colony-stimulating factor (M-CSF) receptor and various leukemogenic tyrosine kinases, such as Bcr-Abl, or NPM-ALK. THOC5 tyrosine phosphorylation is elevated in stem cells from patients with chronic myeloid leukemia, suggesting that THOC5 may be involved in leukemia development. THOC5 is also an essential element in the maintenance of hematopoiesis in adult mice. In this report, we show that THOC5 is located in the nuclear speckles, and that it is translocated from the nucleus to cytoplasm during M-CSF-induced bone marrow-derived macrophage differentiation. Furthermore, we have identified THOC5 target genes by trancriptome analysis, using tamoxifen-inducible THOC5 knockout macrophages. Although only 99 genes were downregulated in THOC5-depleted macrophages, half of the genes are involved in differentiation and/or migration. These include well-known regulators of myeloid differentiation inhibitor of DNA binding (Id)1, Id3, Smad family member 6 (Smad6) and Homeobox (Hox)A1. In addition, a subset of M-CSF-inducible genes, such as Ets family mRNAs are THOC5 target mRNAs. Upon depletion of THOC5, unspliced v-ets erythroblastosis virus E26 oncogene homolog (Ets1) mRNA was accumulated in the nucleus. Furthermore, THOC5 was recruited to chromatin where Ets1 was transcribed and bound to unspliced and spliced Ets1 transcripts, indicating that THOC5 has a role in processing/export of M-CSF-inducible genes. In conclusion, regulation of immediate-early gene response by THOC5, a member of mRNA export complex contributes to the M-CSF-induced macrophage differentiation.
造血和向特定谱系的定向分化受到细胞因子受体及其下游转录因子的调控。mRNA 输出复合物的一个成员，THOC5（高表达 hpr1 delta 转录缺陷抑制物复合物 5）是几种酪氨酸激酶的底物，如巨噬细胞集落刺激因子（M-CSF）受体和各种致白血病酪氨酸激酶，如 Bcr-Abl 或 NPM-ALK。慢性髓性白血病患者的干细胞中 THOC5 的酪氨酸磷酸化水平升高，提示 THOC5 可能参与白血病的发生。THOC5 也是成年小鼠造血维持的重要组成部分。在本报告中，我们发现 THOC5 位于核斑点中，并且在 M-CSF 诱导的骨髓源性巨噬细胞分化过程中从核内易位到细胞质中。此外，我们通过使用他莫昔芬诱导的 THOC5 敲除巨噬细胞进行转录组分析，鉴定了 THOC5 的靶基因。尽管在 THOC5 缺失的巨噬细胞中仅有 99 个基因下调，但其中一半的基因参与分化和/或迁移。这些基因包括 DNA 结合抑制因子（Id）1、Id3、Smad 家族成员 6（Smad6）和 Homeobox（Hox）A1 等已知的髓系分化抑制剂的调节剂。此外，M-CSF 诱导的基因的一个亚群，如 Ets 家族 mRNA，是 THOC5 的靶标 mRNA。THOC5 缺失后，未剪接的 v-ets 红细胞生成病毒 E26 癌基因同源物（Ets1）mRNA 在核内积累。此外，THOC5 被募集到 Ets1 转录和结合未剪接和剪接 Ets1 转录本的染色质上，表明 THOC5 在 M-CSF 诱导的基因的加工/输出中起作用。总之，mRNA 输出复合物的成员 THOC5 对早期基因反应的调节有助于 M-CSF 诱导的巨噬细胞分化。
