END-TO-END TRANSCRIPTION OF AN ALU FAMILY REPEAT - A NEW TYPE OF POLYMERASE-III-DEPENDENT TERMINATOR AND ITS EVOLUTIONARY IMPLICATION
END-TO-END TRANSCRIPTION OF AN ALU FAMILY REPEAT - A NEW TYPE OF POLYMERASE-III-DEPENDENT TERMINATOR AND ITS EVOLUTIONARY IMPLICATION
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DOI：
10.1016/0022-2836(85)90039-7
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发表时间：
1985-01-01
影响因子：
5.6
通讯作者：
SHEN, CKJ
中科院分区：
文献类型：
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作者：
HESS, J;PEREZSTABLE, C;SHEN, CKJ
连续性胸苷残基（≥4)非模板链上的G + C-和侧翼DNA的G + C-丰富性是有效的RNA聚合酶-III依赖性转录终止子的2个必要特征。通过对人类Alu家族重复序列的体外转录研究，发现了一种新型的RNA聚合酶III依赖性转录终止子。位于人α 1珠蛋白基因3 ″侧的258个碱基对的Alu重复序列可以在HeLa S-100提取物中转录，分别产生长度为404-408、252-255和173-174个核苷酸的3种RNA。动力学，脉冲追逐和RNA孵育实验表明，没有显着的内部加工的较长的转录成较短的。这些数据加上详细的RNA图谱最终证明，多个Alu RNA种类是由重复序列的第1个碱基（5“末端）的准确起始和下游的多个终止引起的。主要转录物的3“末端（252-255个核苷酸）定位在Alu重复序列的3”末端，其中不存在≥ 100个核苷酸。非模板链上的4个连续胸苷残基。将终止子的功能结构域定位于45个碱基对的片段，该片段包括Alu重复序列的3“末端序列的36个碱基对加上下游的9个碱基对。高终止效率（> 90%）、缺乏连续的T残基、A + T含量丰富以及RNA在转录物的3“区域中形成不完美发夹结构的能力，因此鉴定了一种新类型的真核III类终止子。将该III类终止子的结构与细菌rho依赖性终止子的结构进行比较。本文还讨论了Alu序列在灵长类基因组中扩增和分散的机制。
Consecutive thymidine residues (.gtoreq. 4) on the non-template strand and G + C- richness of flanking DNA are the 2 necessary characteristics of efficient RNA polymerase-III-dependent transcriptional terminators. From the study of in vitro transcription of a human Alu family repeat, a new type of RNA polymerase-III-dependent transcriptional terminator was identified. A 258 base-pair Alu repeat located on the 3'' side of the human .alpha.1 globin gene can be transcribed in a HeLa S-100 extract to generate 3 RNA species of lengths 404-408, 252-255 and 173-174 nucleotides, respectively. Kinetics, pulse-chase and RNA incubation experiments showed no significant internal processing of the longer transcripts into shorter one. These data plus detailed RNA mapping demonstrated conclusively that the multiple Alu RNA species resulted from accurate initiation at the 1st base (5'' end) of the repeat, and multiple termination downstream. The 3'' end(s) of the major transcript (252-255 nucleotides) maps at the 3'' end of the Alu repeat sequence where there are not .gtoreq. 4 consecutive thymidine residues on the non-template strand. The functional domain of the terminator was mapped to a 45 base-pair segment that includes 36 base-pairs of the 3'' end sequence of the Alu repeat plus 9 base-pairs downstream. The high efficiency of termination (> 90%), the lack of consecutive T residues, the richness in A + T content and the proposed ability of the RNA to form an imperfect hairpin structure in the 3'' region of the transcript thus identify a new type of eukaryotic class III terminator. The structure of this class III terminator is compared with that of the bacterial rho-dependent terminator. Its implication in the mechanism(s) of amplification and dispersion of Alu sequences in the primate genomes is also discussed.