Gbadegesin M A
Department of Biochemistry, Faculty of Basic Medical Sciences, University of Ibadan, Ibadan 200005, Nigeria.
Afr J Med Med Sci. 2012 Dec;41 Suppl:13-25.
In many organisms with large and complex genomes, transposable elements (TEs) constitute up to 50% of the genomic DNA. TEs have been widely studied and they showed high similarities across kingdoms. Several reasons have been adduced for the diverse TEs among plants and animal species. Activities of TEs could give rise to altered gene or genome at very high frequencies in both germinal and somatic tissues. TE-induced genetic variability can range widely; from changes in the arrangement of the whole genome to changes in single nucleotides. This may produce major effects on the phenotypic traits or small silent changes detectable only at the DNA sequence level. TE-induced mutation in the regulatory sequences may be of evolutionary significance and insertions in promoter sequences can alter tissue-specific patterns of gene expression. In addition, transposons can be involved in amplification and dispersal of genes by taking up portions of other sequences within the TEs themselves, moving them to new locations, thereby increasing their copy number. Therefore, mobilization of TEs might benefit the host through enhancement of genetic diversity. However, TE movement have been linked with undesirable traits in plants, hybrid dysgenesis in Drosophila and genome instability and diseases in mammals. This review summarises the diversity of TEs across plant and animal kingdoms and their impact and possible role in genomic evolution. It also describes some adverse effects of TEs as agents of genomic instability and diseases such as cancers, and the genetic regulations of their activities.
在许多拥有庞大而复杂基因组的生物体中，转座元件（TEs）构成了高达50%的基因组DNA。TEs已得到广泛研究，并且在不同生物界中表现出高度相似性。关于动植物物种中转座元件的多样性，人们提出了几个原因。TEs的活性可在生殖组织和体细胞组织中以非常高的频率导致基因或基因组发生改变。TEs诱导的遗传变异范围很广；从整个基因组排列的变化到单核苷酸的变化。这可能对表型性状产生重大影响，或者产生仅在DNA序列水平上可检测到的微小沉默变化。TEs在调控序列中诱导的突变可能具有进化意义，而在启动子序列中的插入可改变基因表达的组织特异性模式。此外，转座子可通过获取自身内部其他序列的部分片段，将它们转移到新位置，从而增加其拷贝数，进而参与基因的扩增和扩散。因此，TEs的移动可能通过增强遗传多样性而使宿主受益。然而，TEs的移动与植物中的不良性状、果蝇中的杂种不育以及哺乳动物中的基因组不稳定性和疾病有关。本综述总结了动植物界中转座元件的多样性及其在基因组进化中的影响和可能作用。它还描述了TEs作为基因组不稳定和癌症等疾病的因素所产生的一些不良影响，以及它们活性的遗传调控。
