Nagel Stefan, Pommerenke Claudia, Meyer Corinna, Kaufmann Maren, Drexler Hans G, MacLeod Roderick A F
Department of Human and Animal Cell Lines, Leibniz-Institute DSMZ - German Collection of Microorganisms and Cell Cultures, Braunschweig, Germany.
Oncotarget. 2016 Jul 19;7(29):45398-45413. doi: 10.18632/oncotarget.9982.
Recently, we identified deregulated expression of the B-cell specific transcription factor MEF2C in T-cell acute lymphoid leukemia (T-ALL). Here, we performed sequence analysis of a regulatory upstream section of MEF2C in T-ALL cell lines which, however, proved devoid of mutations. Unexpectedly, we found strong conservation between the regulatory upstream region of MEF2C (located at chromosomal band 5q14) and an intergenic stretch at 7q11 located between STAG3L4 and AUTS2, covering nearly 20 kb. While the non-coding gene STAG3L4 was inconspicuously expressed, AUTS2 was aberrantly upregulated in 6% of T-ALL patients (public dataset GSE42038) and in 3/24 T-ALL cell lines, two of which represented very immature differentiation stages. AUTS2 expression was higher in normal B-cells than in T-cells, indicating lineage-specific activity in lymphopoiesis. While excluding chromosomal aberrations, examinations of AUTS2 transcriptional regulation in T-ALL cells revealed activation by IL7-IL7R-STAT5-signalling and MEF2C. AUTS2 protein has been shown to interact with polycomb repressor complex 1 subtype 5 (PRC1.5), transforming this particular complex into an activator. Accordingly, expression profiling and functional analyses demonstrated that AUTS2 activated while PCGF5 repressed transcription of NKL homeobox gene MSX1 in T-ALL cells. Forced expression and pharmacological inhibition of EZH2 in addition to H3K27me3 analysis indicated that PRC2 repressed MSX1 as well. Taken together, we found that AUTS2 and MEF2C, despite lying on different chromosomes, share strikingly similar regulatory upstream regions and aberrant expression in T-ALL subsets. Our data implicate chromatin complexes PRC1/AUTS2 and PRC2 in a gene network in T-ALL regulating early lymphoid differentiation.
最近，我们在T细胞急性淋巴细胞白血病（T-ALL）中发现了B细胞特异性转录因子MEF2C的表达失调。在此，我们对T-ALL细胞系中MEF2C的上游调控区进行了序列分析，然而，结果显示该区域没有突变。出乎意料的是，我们发现MEF2C的上游调控区（位于染色体5q14带）与位于STAG3L4和AUTS2之间的7q11基因间区域存在高度保守性，覆盖近20 kb。虽然非编码基因STAG3L4表达不明显，但AUTS2在6%的T-ALL患者（公共数据集GSE42038）和3/24的T-ALL细胞系中异常上调，其中两个细胞系代表非常不成熟的分化阶段。AUTS2在正常B细胞中的表达高于T细胞，表明其在淋巴细胞生成中具有谱系特异性活性。在排除染色体畸变的情况下，对T-ALL细胞中AUTS2转录调控的研究揭示了IL7-IL7R-STAT5信号通路和MEF2C对其的激活作用。已证明AUTS2蛋白与多梳抑制复合物1亚型5（PRC1.5）相互作用，将这种特定复合物转化为激活剂。因此，表达谱分析和功能分析表明，在T-ALL细胞中，AUTS2激活而PCGF5抑制NKL同源盒基因MSX1的转录。除了H3K27me3分析外，EZH2的强制表达和药理学抑制表明PRC2也抑制MSX1。综上所述，我们发现AUTS2和MEF2C尽管位于不同染色体上，但在T-ALL亚群中具有惊人相似的上游调控区和异常表达。我们的数据表明，染色质复合物PRC1/AUTS2和PRC2参与了T-ALL中调节早期淋巴细胞分化的基因网络。
