Liu A Y, Torchia B S, Migeon B R, Siliciano R F
Department of Molecular Biology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
Genomics. 1997 Jan 15;39(2):171-84. doi: 10.1006/geno.1996.4463.
We describe the cloning and characterization of the NTT gene (noncoding transcript in T cells), identified by differential display RT-PCR based on the differential presence of its transcript in a subset of activated, human CD4+ T-cell clones. The full-length cDNA and genomic sequences were cloned and found to produce a 17-kb transcript that is polyadenylated, but is not spliced. Consistent with the transcript's nuclear predominance, NTT has no open reading frame larger than 270 bp. It is transcribed in a select subset of CD4+ T-cell clones propagated in vitro. Its transcription can also be induced in freshly isolated T cells by in vitro activation with PHA or with PMA and ionomycin. In vivo, NTT transcripts are found only in activated, but not resting, T cells. Transcripts were absent in a variety of lymphoid cell lines and transformed lines from other tissues. NTT is a new member of the small group of genes including XIST (X-specific transcript), H19, and IPW (imprinted gene in the Prader-Willi syndrome region), which are transcribed but not translated, and may have a role in the regulation of neighboring genes. XIST, H19, and IPW exhibit monoallelic expression, but both NTT alleles are expressed in CD4+ T-cell clones. Southern blot and fluorescence in situ hybridization analyses show that NTT is a single-copy gene residing in chromosome 6q23-q24, near the interferon-gamma receptor gene (IFN-gamma R). Their proximity and shared expression pattern suggest a possible functional relationship.
我们描述了NTT基因（T细胞中的非编码转录本）的克隆与特性分析，该基因是通过差异显示逆转录聚合酶链反应（RT-PCR）鉴定出来的，其依据是在一部分活化的人CD4+ T细胞克隆中该转录本的差异存在情况。全长互补DNA（cDNA）和基因组序列被克隆出来，发现其产生一个17千碱基的转录本，该转录本是多聚腺苷酸化的，但不进行剪接。与该转录本在细胞核中占主导地位一致，NTT没有大于270碱基对的开放阅读框。它在体外培养的特定CD4+ T细胞克隆亚群中被转录。其转录也可通过用植物血凝素（PHA）或佛波酯（PMA）和离子霉素进行体外活化，在新鲜分离的T细胞中诱导产生。在体内，NTT转录本仅在活化的而非静止的T细胞中被发现。在多种淋巴样细胞系和来自其他组织的转化细胞系中均未发现转录本。NTT是包括XIST（X染色体特异性转录本）、H19和IPW（普拉德-威利综合征区域的印记基因）在内的一小类基因的新成员，这些基因被转录但不被翻译，可能在邻近基因的调控中发挥作用。XIST、H19和IPW表现出单等位基因表达，但在CD4+ T细胞克隆中NTT基因的两个等位基因均表达。Southern印迹和荧光原位杂交分析表明，NTT是位于6号染色体q23-q24区域的单拷贝基因，靠近干扰素-γ受体基因（IFN-γR）。它们的邻近性和共同的表达模式提示可能存在功能关系。
