Ogert R A, Beemon K L
Department of Biology, Johns Hopkins University, Baltimore, Maryland 21218, USA.
J Virol. 1998 Apr;72(4):3407-11. doi: 10.1128/JVI.72.4.3407-3411.1998.
The direct repeat (DR) sequences flanking the src gene in Rous sarcoma virus are essential posttranscriptional control elements; at least one copy of this sequence is necessary for cytoplasmic accumulation of unspliced viral RNA. These sequences promote Rev-independent human immunodeficiency virus type 1 expression, suggesting they act as constitutive transport elements (CTEs). To determine which regions of this sequence are critical for CTE function, mutations in the downstream DR were generated and tested in a viral deletion construct lacking src and the upstream DR. Two single-point mutations and three different clustered mutations caused substantial reductions in reverse transcriptase activity, Gag protein levels, and unspliced viral RNA in the cytoplasm. Three conserved regions of the CTE, including nucleotides 8844 to 8847, 8862 to 8864, and 8868 to 8870, were most sensitive to inactivation by mutagenesis.
劳氏肉瘤病毒src基因侧翼的直接重复（DR）序列是转录后控制的关键元件；该序列的至少一个拷贝对于未剪接病毒RNA在细胞质中的积累是必需的。这些序列促进了不依赖于Rev的1型人类免疫缺陷病毒的表达，表明它们作为组成型转运元件（CTE）发挥作用。为了确定该序列的哪些区域对CTE功能至关重要，在缺少src和上游DR的病毒缺失构建体中产生并测试了下游DR中的突变。两个单点突变和三个不同的簇状突变导致逆转录酶活性、Gag蛋白水平以及细胞质中未剪接病毒RNA的大幅降低。CTE的三个保守区域，包括核苷酸8844至8847、8862至8864以及8868至8870，对诱变失活最为敏感。
