IDENTIFICATION OF INTRINSIC TERMINATION SITES INVITRO FOR RNA POLYMERASE-II WITHIN EUKARYOTIC GENE-SEQUENCES
IDENTIFICATION OF INTRINSIC TERMINATION SITES INVITRO FOR RNA POLYMERASE-II WITHIN EUKARYOTIC GENE-SEQUENCES
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DOI：
10.1016/0022-2836(87)90691-7
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发表时间：
1987-07-20
影响因子：
5.6
通讯作者：
KANE, CM
中科院分区：
文献类型：
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作者：
REINES, D;WELLS, D;KANE, CM
我们已经确定并绘制了几个DNA序列内的人组蛋白基因（H3.3），在体外转录的高度纯化的RNA聚合酶II有效地终止。由于我们系统中的转录仅涉及RNA聚合酶II作用于线性DNA模板，因此这些序列包含由聚合酶蛋白本身识别的“内在”终止信号。基因中存在这样的信号表明，哺乳动物转录单位可能存在有效的抗终止系统。或者，可能存在高频率的过早转录终止，或基因如H3.3的“极性”。H3.3中的内在转录终止位点位于非转录DNA链上的连续胸苷酸残基（5至8个核苷酸）的序列中（T-run），由此，这样的T-run可能是RNA聚合酶II的内在终止信号的元件。然而，转录通过许多类似的T-运行进行而没有显著的终止，由此得出这些内在终止信号包括其他元件。由于当转录物作为DNA-RNA杂合体沿其全长保持沿着结合时，转录也在这些位点有效终止，因此转录物中特异性RNA二级结构的形成不太可能是内在终止信号的一般要素。尽管小鼠β-CD的编码部分下游的DNA序列珠蛋白基因被认为是体内转录终止的位点，这些区域不包含强的内在终止信号，并且体外转录通过这些区域进行几乎不减弱。体内该区域的转录终止可能取决于终止因子或其他细胞内元件的存在，并且可能存在多种控制真核终止的DNA信号。
We have identified and mapped several DNA sequences within a human histone gene (H3.3) at which in-vitro transcription by highly purified RNA polymerase II is efficiently terminated. Since transcription in our system involves only RNA polymerase II acting on a linear DNA template, these sequences contain "intrinsic" termination signals recognized by the polymerase protein itself. The existence of such signals within a gene suggests that efficient antitermination systems probably exist for mammalian transcription units. Alternatively, there could be a high frequency of premature transcription termination, or "polarity" for genes such as H3.3. Intrinsic transcription termination sites in H3.3 are located in sequences of consecutive thymidylate residues (5 to 8 nucleotides) on the non-transcribed DNA strand (T-runs), from which it is likely that such T-runs are elements of the intrinsic termination signal for RNA polymerase II. However, transcription proceeds without significant termination through many similar T-runs, from which it follows that these intrinsic termination signals include other elements. Since transcription is also terminated efficiently at these sites when the transcript remains bound along its full length as a DNA-RNA hybrid, it is unlikely that formation of specific RNA secondary structures in the transcript is a general element of the intrinsic termination signal. Although DNA sequences downstream from the coding portion of the mouse .beta.-globin gene have been implicated as sites of transcription termination in vivo, these regions do not contain strong intrinsic termination signals, and transcription in vitro proceeds through these regions almost undiminished. Transcriptional termination in this region in vivo may depend on the presence of termination factors or other intracellular elements, and there may be multiple classes of DNA signals that control eukaryotic termination.