REGULATION OF HTLV-I GENE EXPRESSION

人T细胞嗜淋巴病毒I型(HTLV-I)编码一个40kD的核 反式激活磷蛋白，Tax1。紫杉醇1基因突变体的分析 证明Tax1(Delta 58)第2至59位氨基酸的缺失 Taxl)减少HTLV-I长末端重复序列10-to的反式激活 20倍。SL核酸酶分析显示， HTLV-I长末端重复序列的反式激活与 缺乏RNA合成。与核局部化形成鲜明对比的是 野生型Taxl蛋白，间接免疫荧光分析证明 Delta58Taxl未能定位到细胞核，表明 紫杉核定位序列存在于氨基酸2至 59.野生型和突变型紫杉醇DNA共转染导致 紫杉醇的细胞质积累和25倍的减少 激活。尽管有几种可能性可以解释 这种跨显性效应存在，我们倾向于Delta 58 Taxi的模式 干扰野生型Taxl蛋白的核定位， 也许是通过形成异二聚体复合体。 C-ETS-I原癌基因与相关的c-ETS-2基因编码相关 与DNA结合的核染色质相关蛋白。去调查 Ets1和Ets2是转录激活因子的可能性，我们 分析了这些蛋白反式激活启动子/增强子的能力 瞬时共转染实验中的序列。HTLV-I LTR是 发现Ets1和Ets2都能反式激活。一个ETS响应 LTR的-117和-160位之间的序列由 HTLV-I LTR5‘端缺失突变体的分析 LTR增强子区域特定基序的二聚化版本。等 被发现与-117到-160的调控序列特异性结合。 这些结果表明Ets1和Ets2是序列特异的转录产物。 功能性激活剂。鉴于Ets1在中国的高水平表达 淋巴样细胞，Etsl可能是转录复合体的一部分， 介导对Taxl的应答和HTLV-I复制的控制。

Human T-cell lymphotropic virus type I (HTLV-I) encodes a 40-kD nuclear trans-activating phosphoprotein, Tax1. The analysis of Tax1 mutants demonstrates that deletion of amino acids 2 through 59 of Taxl (delta 58 Taxl) decreased transactivation of the HTLV-I long terminal repeat 10- to 20-fold. Sl nuclease analysis revealed that the decrease in transactivation of the HTLV-I long terminal repeat was associated with a lack of RNA synthesis. In contrast to the nuclear localization of the wild-type Taxl protein, indirect immunofluorescence analysis demonstrated that delta 58 Taxl failed to localize to the nucleus, indicating that the Taxl nuclear localization sequence is present in amino acids 2 through 59. Cotransfection of wild-type and mutant Taxl DNAs resulted in the cytoplasmic accumulation of Taxl and a 25-fold decrease in transactivation. Although several possibilities which may account for this transdominant effect exist, we favor a model in which delta 58 Taxl interferes with the nuclear localization of wild-type Taxl protein, perhaps by forming heterodimer complexes. The c-ets-I proto-oncogene and the related c-ets-2 gene encode related nuclear chromatin-associated proteins which bind DNA in . To investigate the possibility that Etsl and Ets2 are transcriptional activators, we analyzed the ability of these proteins to transactivate promoter/enhancer sequences in transient co-transfection experiments. The HTLV-I LTR was found to be transactivated by both Etsl and Ets2. An ets-responsive sequence between positions -117 and -160 of the LTR was identified by analyses of a series of 5' deletion mutants of the HTLV-I LTR and of dimerized versions of specific motifs of the LTR enhancer region. Etsl was found to bind specifically to the -117 to -160 regulatory sequence. These results show that Etsl and Ets2 are sequence-specific transcrip- tional activators. In view of the high level expression of Etsl in lymphoid cells, Etsl could be part of the transcription complex which mediates the response to Taxl and the control of HTLV-I replication.