Duan Xiao-Cui, Jin Xia, Xie Ying, Jiao Ning, Liu Jing, Wang Xiao-Yan, Lu Zhan-Jun
Hebei Key Lab of Laboratory Animal, Department of Genetics, Hebei Medical University, Shijiazhuang 050017, China.
Yi Chuan. 2009 Jan;31(1):50-6. doi: 10.3724/sp.j.1005.2009.00050.
An intact L1 define element is 6 kb in length in human genome. The majority of the L1s is truncated and has direction difference, implying that it is interesting to study the effects of different length and directions of L1s on gene. In this work, 7 different segments were obtained from L1-open reading frame 2 (ORF2), each of which was 280 bp in length. Each segment was connected into 8 repeats in head and tail tandem manner and was inserted to downstream of GFP gene in different directions in pEGFP-C1. The inserted ORF2 segments in the sense orientation caused much stronger inhibition on gene transcription and protein expression than antisense sequences did. Among all segments, the first and ninth 280 bp segments of ORF2 in both orientations induced weaker inhibition on gene transcription than other segments in the same orientations and did not induce transcriptional elongation. The distribution of Alu in most regions of genome was inverse ratio with L1. The inserted Alus in both orientations inhibited GFP gene expression, but the inhibition in antisense orientation was stronger than that in sense orientation and the sense Alu was the sequence of inducing transcription elongation. A-rich of ORF2 was probably the molecular basis of its sense orientation with stronger inhibition on gene expression.
在人类基因组中，完整的L1定义元件长度为6 kb。大多数L1是截短的且存在方向差异，这意味着研究不同长度和方向的L1对基因的影响具有重要意义。在本研究中，从L1开放阅读框2（ORF2）获得了7个不同片段，每个片段长度为280 bp。每个片段以首尾串联的方式连接成8个重复，并以不同方向插入到pEGFP-C1中GFP基因的下游。正义方向插入的ORF2片段对基因转录和蛋白质表达的抑制作用比反义序列更强。在所有片段中，两个方向的ORF2的第一个和第九个280 bp片段在相同方向上对基因转录的抑制作用比其他片段弱，且不诱导转录延伸。基因组大多数区域中Alu的分布与L1呈反比。两个方向插入的Alu均抑制GFP基因表达，但反义方向的抑制作用比正义方向更强，且正义Alu是诱导转录延伸的序列。ORF2富含A可能是其正义方向对基因表达具有更强抑制作用的分子基础。
