Izsvák Z, Ivics Z, Shimoda N, Mohn D, Okamoto H, Hackett P B
Department of Genetics & Cell Biology, University of Minnesota, 1445 Gortner Avenue, St. Paul, MN 55108-1095, USA.
J Mol Evol. 1999 Jan;48(1):13-21. doi: 10.1007/pl00006440.
Angel is the first miniature inverted-repeat transposable element (MITE) isolated from fish. Angel elements are imperfect palindromes with the potential to form stem-loop structures in vitro. Despite sequence divergence of elements of up to 55% within and between species, their inverted repeat structures have been maintained, implying functional importance. We estimate that there are about 10(3)-10(4) Angels scattered throughout the zebrafish genome, evidence that this family of transposable elements has been significantly amplified over the course of evolution. Angel elements and Xenopus MITEs carry common sequence motifs at their termini, indicating common origin and/or related mechanisms of transposition. We present a model in which MITEs take advantage of the basic cellular mechanism of DNA replication for their amplification, which is dependent on the characteristic inverted repeat structures of these elements. We propose that MITEs are genomic parasites that transpose via a DNA intermediate, which forms by a folding-back of a single strand of DNA, that borrow all of the necessary factors for their amplification from products encoded in the genomes in which they reside. DNA polymorphisms in different lines of zebrafish were detected by PCR using Angel-specific primers, indicating that such elements, combined with other transposons in vertebrate genomes, will be useful molecular tools for genome mapping and genetic analyses of mutations.
Angel是从鱼类中分离出的首个微型反向重复转座元件（MITE）。Angel元件是不完全回文序列，在体外有形成茎环结构的潜力。尽管物种内部和物种之间元件的序列差异高达55%，但其反向重复结构仍得以保留，这暗示了其功能上的重要性。我们估计在斑马鱼基因组中散布着约10³ - 10⁴个Angel元件，这证明该转座元件家族在进化过程中已显著扩增。Angel元件和非洲爪蟾MITEs在其末端带有共同的序列基序，表明它们有共同的起源和/或相关的转座机制。我们提出了一个模型，其中MITEs利用DNA复制的基本细胞机制进行扩增，这依赖于这些元件特有的反向重复结构。我们认为MITEs是通过DNA中间体进行转座的基因组寄生虫，该中间体由单链DNA回折形成，它们从自身所在基因组中编码的产物借用所有扩增所需的必要因子。使用Angel特异性引物通过PCR检测了不同斑马鱼品系中的DNA多态性，这表明此类元件与脊椎动物基因组中的其他转座子相结合，将成为用于基因组作图和突变遗传分析的有用分子工具。
