Rotman G, Itin A, Keshet E
Nucleic Acids Res. 1986 Jan 24;14(2):645-58. doi: 10.1093/nar/14.2.645.
LTR units associated with cellular retrovirus-like elements are abundantly present in chromosomal DNA of animal cells. We have analyzed the promoter and enhancer activities of diverse LTR units associated with different members of the murine retrovirus-like family known as VL30. We report here that the structurally heterogenous VL30 LTRs displayed highly variable promoter/enhancer activities. The most active VL30 LTR (designated VL3) promoted CAT activity to levels six-fold higher than the LTR of the strongly transforming retrovirus, MSV. This VL30 transcription unit, containing a unique U3 region, was further characterized by S1 nuclease mapping. VL3 LTR functioned as an enhancer in CAT constructs containing a SV40 promoter. In addition, a defined U3 segment was shown to augment expression of CAT in an orientation independent manner. VL3 LTR also served as an efficient promoter and enhancer in heterologous monkey cells. These results suggest that certain resident LTRs possess promoter and enhancer capacities greater than those possessed by LTRs of infectious retroviruses.
与细胞逆转录病毒样元件相关的长末端重复序列（LTR）大量存在于动物细胞的染色体DNA中。我们分析了与小鼠逆转录病毒样家族不同成员（称为VL30）相关的多种LTR的启动子和增强子活性。我们在此报告，结构异质的VL30 LTR显示出高度可变的启动子/增强子活性。最活跃的VL30 LTR（命名为VL3）将氯霉素乙酰转移酶（CAT）活性提高到比强转化逆转录病毒MSV的LTR高六倍的水平。这个包含独特U3区域的VL30转录单位通过S1核酸酶图谱进一步表征。VL3 LTR在含有SV40启动子的CAT构建体中起增强子作用。此外，一个确定的U3片段被证明以方向独立的方式增强CAT的表达。VL3 LTR在异源猴细胞中也作为有效的启动子和增强子。这些结果表明，某些常驻LTR具有比感染性逆转录病毒的LTR更大的启动子和增强子能力。
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