Chow L T, Gelinas R E, Broker T R, Roberts R J
Cell. 1977 Sep;12(1):1-8. doi: 10.1016/0092-8674(77)90180-5.
The 5' terminal sequences of several adenovirus 2 (Ad2) mRNAs, isolated late in infection, are complementary to sequences within the Ad2 genome which are remote from the DNA from which the main coding sequence of each mRNA is transcribed. This has been observed by forming RNA displacement loops (R loops) between Ad2 DNA and unfractionated polysomal RNA from infected cells. The 5' terminal sequences of mRNAs in R loops, variously located between positions 36 and 92, form complex secondary hybrids with single-stranded DNA from restriction endonuclease fragments containing sequences to the left of position 36 on the Ad2 genome. The structures visualized in the electron microscope show that short sequences coded at map positions 16.6, 19.6 and 26.6 on the R strand are joined to form a leader sequence of 150-200 nucleotides at the 5' end of many late mRNAs. A late mRNA which maps to the left of position 16.6 shows a different pattern of second site hybridization. It contains sequences from 4.9-6.0 linked directly to those from 9.6-10.9. These findings imply a new mechanism for the biosynthesis of Ad2 mRNA in mammalian cells.
在感染后期分离得到的几种腺病毒2（Ad2）mRNA的5'末端序列，与Ad2基因组内远离各mRNA主要编码序列转录所依据的DNA的序列互补。这一现象是通过在Ad2 DNA与来自感染细胞的未分级多聚核糖体RNA之间形成RNA置换环（R环）观察到的。R环中mRNA的5'末端序列位于36至92位之间的不同位置，它们与来自包含Ad2基因组36位左侧序列的限制性内切酶片段的单链DNA形成复杂的二级杂交体。电子显微镜下观察到的结构表明，在R链上位于图谱位置16.6、19.6和26.6编码的短序列连接在一起，在许多晚期mRNA的5'末端形成一个150 - 200个核苷酸的前导序列。一个位于16.6位左侧的晚期mRNA显示出不同的第二位点杂交模式。它包含直接与9.6 - 10.9的序列相连的4.9 - 6.0的序列。这些发现暗示了哺乳动物细胞中Ad2 mRNA生物合成的一种新机制。
