Horowitz J M, Holland G D, King S R, Risser R
J Virol. 1987 Mar;61(3):701-7. doi: 10.1128/JVI.61.3.701-707.1987.
Nucleotide sequence analysis of the cellular sequences flanking the integrated ecotropic (mouse-infectious) murine leukemia provirus of BALB/c mice indicated that the murine leukemia provirus is integrated in opposing transcriptional orientation within a solo long terminal repeat (LTR) of the VL30 family of endogenous retrovirus-related sequences. To quantify the effect of this integration event on the ability of the ecotropic provirus to be expressed, we constructed recombinant molecules that carried the chloramphenicol acetyltransferase (cat) gene and various viral LTRs and determined the CAT activity induced by these constructs after transfection of NIH 3T3 cells. Our results indicate that the BALB/c ecotropic LTR is about 10-fold more active than the VL30 LTR. The presence of the VL30 LTR did not affect the transcriptional activity of the ecotropic LTR in the context of the integration event. Our results also indicate that the LTRs of the BALB/c provirus are less transcriptionally active than are the proviral LTRs of AKR murine leukemia virus and the Harvey murine sarcoma virus.
对BALB/c小鼠整合的亲嗜性（感染小鼠）鼠白血病前病毒两侧的细胞序列进行核苷酸序列分析表明，鼠白血病前病毒以相反的转录方向整合在内源性逆转录病毒相关序列的VL30家族的单个长末端重复序列（LTR）内。为了量化这一整合事件对亲嗜性前病毒表达能力的影响，我们构建了携带氯霉素乙酰转移酶（cat）基因和各种病毒LTR的重组分子，并在转染NIH 3T3细胞后测定了这些构建体诱导的CAT活性。我们的结果表明，BALB/c亲嗜性LTR的活性比VL30 LTR高约10倍。在整合事件的背景下，VL30 LTR的存在并不影响亲嗜性LTR的转录活性。我们的结果还表明，BALB/c前病毒的LTR转录活性低于AKR鼠白血病病毒和哈维鼠肉瘤病毒的前病毒LTR。
