Immunogenetic division, Federal University of São Paulo (UNIFESP), São Paulo, SP, Brazil.
Eur Cytokine Netw. 2010 Dec;21(4):308-18. doi: 10.1684/ecn.2010.0218. Epub 2010 Nov 24.
The human IL-15RA gene encoding the alpha chain of the IL-15 receptor is expressed in a variety of immune and non-immune cell types from different tissues, and generates multiple splicing events of functional importance. We aimed to evaluate expression of IL-15RA transcripts generated by alternative usage of transcription start site (Var1 and Var2) and by deletion of exon 3 (Del3), exon 2 (Del2), or both (Del2,3) in different human tissues. Since a CpG island was found near to the IL-15RA gene transcription start site, we also investigated the role of DNA methylation on the expression of IL-15RA full-length and alternative transcripts fragments in peripheral blood mononuclear cells (PBMC). IL-15RA transcription of functional (full-length and del 3) and non-functional (del 2 and del 2,3) variants was detected in many tissues, however, the number of different IL-15RA transcripts variants detected in each tissue did not correlate with the level of gene expression. IL-15RA transcript variants Var1 and Var2 presented similar expression levels in different human tissues. However, we found a distinct expression profile of functional and non-functional IL-15RA transcripts fragments. A preferential expression of transcripts that bind IL-15 compared to IL-15 non-binding transcripts was seen in the tissues investigated. When PBMC cultures were treated with 5-azacitidine (AZA), a DNA methyltransferase inhibitor, we detected a significant increase in IL-15RA copy number. Only alternative exon skipping events of Var1 (Del 2, Del 3 and Del 2, 3) were altered by AZA treatment, which is consistent with the CpG island localization in the regulatory region 5' upstream of the transcription start site of Var1 and not of Var2. Therefore, this work shows a broad expression pattern of functional IL-15RA splicing forms and suggests a regulatory role of DNA methylation in IL-15RA transcript Var1 expression in mononuclear cells.
人类白细胞介素 15 受体的 alpha 链（IL-15RA）基因的编码序列在不同组织来源的多种免疫细胞和非免疫细胞中表达，并产生多种具有重要功能的剪接事件。本研究旨在评估白细胞介素 15 受体 alpha 链（IL-15RA）转录本在不同人类组织中通过不同转录起始位点（Var1 和 Var2）的使用和通过外显子 3（Del3）、外显子 2（Del2）或两者（Del2,3）的缺失而产生的表达情况。由于在 IL-15RA 基因转录起始位点附近发现了一个 CpG 岛，我们还研究了 DNA 甲基化对外周血单个核细胞（PBMC）中 IL-15RA 全长和替代转录本片段表达的影响。在许多组织中检测到功能性（全长和 Del3）和非功能性（Del2 和 Del2,3）变体的 IL-15RA 转录，但在每种组织中检测到的不同 IL-15RA 转录本变体的数量与基因表达水平无关。在不同的人类组织中，IL-15RA 转录本变体 Var1 和 Var2 的表达水平相似。然而，我们发现功能性和非功能性 IL-15RA 转录本片段的表达谱存在明显差异。在所研究的组织中，与结合 IL-15 的转录本相比，观察到非结合 IL-15 的转录本的表达偏好。当用 5-氮杂胞苷（AZA）处理 PBMC 培养物时，我们检测到 IL-15RA 拷贝数显著增加。只有 Var1 的替代外显子跳跃事件（Del2、Del3 和 Del2,3）被 AZA 处理改变，这与 Var1 转录起始位点上游调控区 5'端的 CpG 岛定位一致，而不是 Var2。因此，本研究表明功能性 IL-15RA 剪接形式具有广泛的表达模式，并提示 DNA 甲基化在单核细胞中 IL-15RA 转录本 Var1 表达中的调节作用。
