Direct evidence that p40x of human T‐cell leukemia virus type I is a trans‐acting transcriptional activator.
Direct evidence that p40x of human T‐cell leukemia virus type I is a trans‐acting transcriptional activator.
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DOI：
10.1002/j.1460-2075.1986.tb04247.x
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发表时间：
1986-03
期刊：
影响因子：
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通讯作者：
M. Seiki;J. Inoue;T. Takeda;M. Yoshida
中科院分区：
文献类型：
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作者：
M. Seiki;J. Inoue;T. Takeda;M. Yoshida
人类T细胞白血病病毒I型在env基因和3′LTR（长末端重复序列）之间有一个独特的序列pX。该序列编码p40 x，其被提议从LTR反式激活转录。最近，我们发现了由框架III编码的新型pX蛋白，其主要与框架IV（x-lor，编码p40 x）重叠，在一个区域也与框架II重叠。为了确定哪种产物负责反式作用功能，我们构建了一个活性前病毒克隆pMTPX，其中包含env、pX和3′LTR的基因组片段，并将定点突变引入活性位点。通过共转染试验处理区分每个重叠开放阅读框（ORF）II、III和IV的各种缺失和点突变对pLTR-CAT反式激活的影响。结果表明，只有影响p40 x表达的突变导致转录激活活性的丧失。这些发现清楚地表明，由框架IV编码的p40 x负责LTR的转录激活。pX mRNA cDNA表达的研究证实了这一结论。
Human T‐cell leukemia virus type I has a unique sequence, pX, between the env gene and the 3′LTR (long terminal repeat). This sequence codes for p40x, which was proposed to trans‐activate transcription from the LTR. Recently, we identified novel pX proteins coded by frame III, which mostly overlaps frame IV (x‐lor, coding for p40x), in a region also overlapped by frame II. To determine which product is responsible for the trans‐acting function, we constructed an active provirus clone, pMTPX, that contained a genomic fragment of the env, pX and 3′LTR, and introduced site‐directed mutations into the active site. The effects of various deletions and point mutations that distinguished each of the overlapping open reading frames (ORFs), II, III and IV, on trans‐activation of pLTR‐CAT were treated by co‐transfection assays. The results showed that only mutations which affected p40x expression resulted in loss of activity for transcriptional activation. These findings clearly indicate that p40x coded by frame IV is responsible for the transcriptional activation of the LTR. This conclusion was confirmed by studies on expression of cDNA of pX mRNA.