Functional and defective components of avian endogenous virus long terminal repeat enhancer sequences.
Functional and defective components of avian endogenous virus long terminal repeat enhancer sequences.
复制标题
禽内源性病毒长末端重复增强子序列的功能性和缺陷性成分。
DOI：
10.1128/jvi.67.3.1545-1554.1993
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发表时间：
1993
影响因子：
5.4
通讯作者：
Conklin,KF
中科院分区：
文献类型：
--
作者：
Habel,DE;Dohrer,KL;Conklin,KF
致癌性禽类逆转录病毒，如劳斯肉瘤病毒（RSV）和禽类白血病病毒，在前病毒长末端重复序列（LTR）的U3部分中含有强增强子。第二类禽类逆转录病毒的LTR，内源性病毒（ev）缺乏可检测的增强子活性。通过创建ev-RSV杂合LTR，我们先前证明，尽管在ev U3区域中缺乏独立的增强子活性，但ev LTR含有能够在功能上取代RSV增强子的必需增强子结构域的序列。为解释这些数据而提出的假设是ev LTR含有部分增强子，所述部分增强子包括增强子活性所必需但不足够的序列，并且这些序列由原始杂合构建体中存在的RSV增强子结构域补充以产生功能性增强子。本报告中描述的研究旨在确定产生该复合增强子所需的ev和RSV LTR的序列。这是通过产生额外的ev-RSV杂合LTR来实现的，所述杂合LTR在ev和RSV之间交换限定的区域，并且通过定点诱变直接测试对特定基序的需求。获得的结果表明，ev增强子序列存在于与RSV的上游增强子序列相同的相对位置，它们与RSV共享有限的序列相似性。此外，鉴定了来自RSV LTR内部的67-bp区域，其是互补ev增强子序列所需的。最后，数据显示，CArG基序是必不可少的高水平的活动，以前没有被证明为逆转录病毒LTR的发现，提出。
Oncogenic avian retroviruses, such as Rous sarcoma virus (RSV) and the avian leukosis viruses, contain a strong enhancer in the U3 portion of the proviral long terminal repeat (LTR). The LTRs of a second class of avian retroviruses, the endogenous viruses (ev) lack detectable enhancer activity. By creating ev-RSV hybrid LTRs, we previously demonstrated that, despite the lack of independent enhancer activity in the ev U3 region, ev LTRs contain sequences that are able to functionally replace essential enhancer domains from the RSV enhancer. A hypothesis proposed to explain these data was that ev LTRs contain a partial enhancer that includes sequences necessary but not sufficient for enhancer activity and that these sequences were complemented by RSV enhancer domains present in the original hybrid constructs to generate a functional enhancer. Studies described in this report were designed to define sequences from both the ev and RSV LTRs required to generate this composite enhancer. This was approached by generating additional ev-RSV hybrid LTRs that exchanged defined regions between ev and RSV and by directly testing the requirement for specific motifs by site-directed mutagenesis. Results obtained demonstrate that ev enhancer sequences are present in the same relative location as upstream enhancer sequences from RSV, with which they share limited sequence similarity. In addition, a 67-bp region from the internal portion of the RSV LTR that is required to complement ev enhancer sequences was identified. Finally, data showing that CArG motifs are essential for high-level activity, a finding that has not been previously demonstrated for retroviral LTRs, are presented.