Adega F, Guedes-Pinto H, Chaves R
Institute for Biotechnology and Bioengineering, Centre of Genetics and Biotechnology, University of Trás-os-Montes and Alto Douro, Vila Real, Portugal.
Cytogenet Genome Res. 2009;126(1-2):12-20. doi: 10.1159/000245903. Epub 2009 Dec 9.
Eukaryotic genomes contain far more DNA than needed for coding proteins. Some of these additional DNA sequences comprise non-coding repetitive DNA sequences, mostly satellite DNAs and also transposable elements usually located at the heterochromatic regions of chromosomes. Satellite DNAs consist of tandemly repeated DNA sequences inhabiting the mammalian genome, typically organized in long arrays of hundreds or thousands of copies. Different important functions have been ascribed to satellite DNA, from the imperative centromeric function in mitosis and meiosis to the recent discovery of its involvement in regulatory functions via satellite transcripts. Moreover, satellite DNAs, among other repetitive sequences, are believed to be the 'engine' triggering mammalian genome evolution. Repetitive DNAs are, most likely, the genetic factors responsible for promoting genomic plasticity and therefore higher rates of chromosome mutation. Furthermore, constitutive heterochromatin regions are thought to be 'hotspots' for structural chromosome rearrangements. A considerable collection of evidences places these sequences in the landscape of mammalian evolution. However, the mechanisms that could explain how this alliance between chromosome evolution and satellite DNA is made are still enigmatic and subject of debate. Throughout the mammalian taxa, different patterns of chromosome evolution have been widely registered from heterochromatin additions/eliminations, Robertsonian translocations, whole-arm reciprocal translocations to tandem translocations; the fact is genome's repetitive fraction is playing a central role in mammalian genome structuring. Throughout this review we will focus on the evidences that associate satellite DNAs and constitutive heterochromatin to the process of chromosome evolution and consequently to domestic species genome's remodeling.
真核生物基因组所含的DNA远远超过编码蛋白质所需的量。这些额外的DNA序列中有些包含非编码重复DNA序列，主要是卫星DNA，还有通常位于染色体异染色质区域的转座元件。卫星DNA由串联重复的DNA序列组成，存在于哺乳动物基因组中，通常以数百或数千个拷贝的长阵列形式组织。卫星DNA被赋予了不同的重要功能，从有丝分裂和减数分裂中至关重要的着丝粒功能到最近发现其通过卫星转录本参与调控功能。此外，卫星DNA与其他重复序列一起，被认为是触发哺乳动物基因组进化的“引擎”。重复DNA很可能是促进基因组可塑性从而导致更高染色体突变率的遗传因素。此外，组成型异染色质区域被认为是染色体结构重排的“热点”。大量证据将这些序列置于哺乳动物进化的图景中。然而，能够解释染色体进化与卫星DNA之间这种关联是如何形成的机制仍然是个谜，也是争论的主题。在整个哺乳动物分类群中，从异染色质的添加/消除、罗伯逊易位、全臂相互易位到串联易位，已经广泛记录了不同的染色体进化模式；事实是基因组的重复部分在哺乳动物基因组结构形成中起着核心作用。在这篇综述中，我们将专注于将卫星DNA和组成型异染色质与染色体进化过程以及由此导致的家养物种基因组重塑联系起来的证据。
