Strand-specific LINE-1 transcription in mouse F9 cells originates from the youngest phylogenetic subgroup of LINE-1 elements.
Strand-specific LINE-1 transcription in mouse F9 cells originates from the youngest phylogenetic subgroup of LINE-1 elements.
复制标题
小鼠 F9 细胞中链特异性 LINE-1 转录源自 LINE-1 元件最年轻的系统发育亚组。
DOI：
10.1016/0022-2836(92)90544-t
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发表时间：
1992
影响因子：
5.6
通讯作者：
Hutchison3rd,CA
中科院分区：
文献类型：
--
作者：
Schichman,SA;Severynse,DM;Edgell,MH;Hutchison3rd,CA
LINE-1 （L1）是一个哺乳动物家族的高度重复的DNA序列，是一类转座元件的成员，其运动涉及RNA中间体。结构和进化数据表明，L1家族由少量活跃的转座元件和大量L1假基因组成。在小鼠中，最长的特征L1序列跨越约7000个碱基对，包含两个长长的开放阅读框。根据在5 '端发现的推定转录调控序列的类型，已经定义了小鼠L1元件的两个亚家族，A和F。为了鉴定小鼠F9畸胎癌细胞中L1元件的转录亚群，我们通过Northern分析检测了L1转录的链特异性，并将10个a型cdna的开放阅读框-1序列与15个基因组a型L1元件进行了比较。含有a型序列的转录本远比含有f型序列的转录本丰富。尽管F9细胞中的大部分L1 RNA似乎都是由两条链非特异性转录的，但我们的研究结果为a型转录调控序列产生的可变长度、链特异性转录物的亚群提供了证据。F9细胞cDNA序列具有99.5%以上的序列同源性，代表了基因组L1群体的一个同质子集。对小鼠基因组L1序列的检查揭示了在第一开放阅读框的定义片段中存在三种类型的长度多态性。系统发育分析表明，第一开放阅读框长度多态性类型与单个a型基因组L1元件的相对年龄之间存在相关性。cDNA和基因组序列的比较表明，a型L1元件的最年轻亚群在F9细胞中优先转录。这一亚群目前可能主导着小鼠L1的扩散过程。
LINE-1 (L1) is a mammalian family of highly repeated DNA sequences that are members of a class of transposable elements whose movement involves an RNA intermediate. Both structural and evolutionary data indicate that the L1 family consists of a small number of active transposable elements interspersed with a large number of L1 pseudogenes. In the mouse, the longest, characterized L1 sequences span about 7000 base-pairs and contain two long open reading frames. Two subfamilies of mouse L1 elements, A and F, have been defined on the basis of the type of putative transcriptional regulatory sequence found at the 5′ end. In order to identify a transcribed subset of L1 elements in mouse F9 teratocarcinoma cells, we have examined the strand-specificity of L1 transcription by Northern analysis and compared the open reading frame-1 sequences of ten A-type cDNAs with fifteen genomic A-type L1 elements. Transcripts containing A-type sequence are far more abundant than those containing F-type sequence. Although the majority of L1 RNA in F9 cells appears to be transcribed non-specifically from both strands, our results provide evidence for a subpopulation of variable length, strand-specific transcripts arising from A-type transcriptional regulatory sequences. F9 cell cDNA sequences, which share greater than 99.5 % sequence identity with one another, represent a homogeneous subset of the genomic L1 population. Examination of genomic mouse L1 sequences reveals three types of length polymorphism in a defined segment of the first open reading frame. Phylogenetic analysis shows a correlation between the type of length polymorphism in the first open reading frame and the relative age of an individual A-type genomic L1 element. Comparison of the cDNA and genomic sequences indicates that the youngest subgroup of A-type L1 elements is preferentially transcribed in F9 cells. This subgroup may be currently dominating the L1 dispersal process in mice.