A HIGHLY REITERATED FAMILY OF TRANSCRIBED OLIGO(A)-TERMINATED, INTERSPERSED DNA ELEMENTS IN THE GENOME OF BOMBYX-MORI
A HIGHLY REITERATED FAMILY OF TRANSCRIBED OLIGO(A)-TERMINATED, INTERSPERSED DNA ELEMENTS IN THE GENOME OF BOMBYX-MORI
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DOI：
10.1016/0022-2836(86)90327-x
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发表时间：
1986-02-20
影响因子：
5.6
通讯作者：
LIZARDI, PM
中科院分区：
文献类型：
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作者：
ADAMS, DS;EICKBUSH, TH;LIZARDI, PM
利用家蚕低Cot DNA （Cot是DNA的摩尔浓度乘以孵育时间，单位为秒）文库，从家蚕基因组中分离出5个高度重复序列的独立克隆。序列分析表明，5个克隆均属于一个重复DNA元件家族，我们将其命名为Bm1，其重复频率约为2.3次。每个单倍体基因组有104个拷贝。用Bm1克隆探测家蚕基因组文库（在λ噬菌体中）显示，该重复序列分散在整个基因组中。采用Southern blot方法对大样本（270.7倍）进行标记，证实了斑点的分布模式。103碱基对)结构域，其中至少有13个独立的区域被发现与Bm1杂交。另外4个Bm1元素从4.8倍测序。含有早期绒毛膜基因的103碱基对基因组片段。这四个元素中的两个由短的（4到12个碱基对）直接重复组成。已测序的9个Bm1元素同源性大于88%，且至少属于两个大小类别（253个碱基对和450个碱基对）。9个Bm1元素中有7个在3'端有一个短的6到10个碱基对的寡核苷酸(a)序列。包括寡核苷酸(A)在内的3”端约29个碱基对序列与人类Alu家族重复元件的等效3”端域有86%的同源性。Bm1 5'端129碱基对结构域与果蝇缬氨酸转移RNA基因同源性为66%；因此，BM1的5'末端可能含有分裂的内部RNA聚合酶III启动子，这是大多数转录的trna样反转录子的特征。家蚕RNA的Dot-blot分析表明，Bm1 DNA确实被转录，并且转录本在5龄早期卵巢来源的永久细胞系和后丝腺的总RNA中有很好的表达，但在5龄后期的蛹或丝腺的RNA中含量较少。
A library of low Cot DNA (Cot is the molar concentration of DNA times the incubation time in seconds) from Bombyx mori was used to isolate five independent clones of highly reiterated sequences from the genome of this organism. Sequence analysis revealed that all five clones belong to a single family of repetitive DNA elements, which we have named Bm1, and whose reiteration frequency is approximately 2.3 .times. 104 copies per haploid genome. Probing of a Bombyx genomic library (in lambda phage) with a Bm1 clone reveals that this repetitive sequence is dispersed throughout the genome. The pattern of interspersion was confirmed by Southern blot mapping of a large (270 .times. 103 base-pairs) domain of the chorion locus of Bombyx, where at least 13 independent regions were found to hybridize to Bm1. Four additional Bm1 elements have been sequenced from a 4.8 .times. 103 base-pair genomic fragment containing an early chorion gene. Two of these four elements are bounded by short (4 to 12 base-pairs) direct repeats. The nine Bm1 elements which have been sequenced are greater than 88% homologous to each other, and tend to fall in at least two size classes (253 base-pairs and 450 base-pairs). Seven of the nine Bm1 elements have a short 6 to 10 base-pair oligo(A) sequence at the 3'' end. A sequence of about 29 base pairs at the 3'' end, including the oligo(A), shows 86% homology to the equivalent 3''-terminal domain of human Alu family repetitive elements. A 129 base-pair domain at the 5'' end of Bm1 shows 66% homology to a Drosophila valine transfer RNA gene; thus the 5'' end of BM1 may contain the split internal RNA polymerase III promoter that is characteristic of most transcribed tRNA-like retroposons. Dot-blot analysis of Bombyx RNA shows that Bm1 DNA is indeed transcribed, and that the transcripts are well-represented in the total RNA of an ovarian-derived permanent cell line and posterior silk glands early in the fifth instar, but are less abundant in the RNA of pupae or silk glands late in the fifth instar.