Jeang K T, Boros I, Brady J, Radonovich M, Khoury G
Laboratory of Molecular Virology, National Cancer Institute, Bethesda, Maryland 20892.
J Virol. 1988 Dec;62(12):4499-509. doi: 10.1128/JVI.62.12.4499-4509.1988.
Transcriptional activation of the human T-cell leukemia virus type I (HTLV-I) long terminal repeat (LTR) by viral protein p40x requires a 21-base-pair (bp) sequence which is repeated three times within the LTR. This sequence contains a core octanucleotide (TGACGTCT) which has been attributed to be a cyclic-AMP (cAMP)-responsive element. We demonstrate here that the HTLV-I LTR can be specifically stimulated by cAMP regulators and have identified four proteins in HeLa cells that bind to the HTLV-I 21-bp sequence. We correlated the in vitro binding and transcriptional activity of one of these cellular factors (Mr, 180,000) to the trans-activation of the HTLV-I LTR by p40x. Point mutations were generated within the cAMP octanucleotide of the HTLV-I 21-bp sequence that simultaneously abolished biological responsiveness to trans-activation by p40x and to stimulation by cAMP. We found that these mutations also eliminated the binding of the 180-kilodalton HeLa factor to the HTLV-I 21-bp element. In the absence of a demonstrable DNA-binding property for p40x, we hypothesize that cellular proteins are involved, possibly through signal transduction pathways, in its trans-activation of responsive promoters.
病毒蛋白p40x对人I型T细胞白血病病毒（HTLV-I）长末端重复序列（LTR）的转录激活需要一个21碱基对（bp）的序列，该序列在LTR内重复三次。这个序列包含一个核心八聚体核苷酸（TGACGTCT），它被认为是一个环磷酸腺苷（cAMP）反应元件。我们在此证明HTLV-I LTR可被cAMP调节剂特异性刺激，并已在HeLa细胞中鉴定出四种与HTLV-I 21-bp序列结合的蛋白质。我们将其中一种细胞因子（分子量为180,000）的体外结合和转录活性与p40x对HTLV-I LTR的反式激活相关联。在HTLV-I 21-bp序列的cAMP八聚体核苷酸内产生点突变，这些突变同时消除了对p40x反式激活和cAMP刺激的生物学反应性。我们发现这些突变也消除了180-kDa的HeLa因子与HTLV-I 21-bp元件的结合。由于未证明p40x具有DNA结合特性，我们推测细胞蛋白可能通过信号转导途径参与其对反应性启动子的反式激活。
