Hasson Dan, Alonso Alicia, Cheung Fanny, Tepperberg James H, Papenhausen Peter R, Engelen John J M, Warburton Peter E
Department of Genetics and Genomic Sciences, Mount Sinai School of Medicine, Icahn Medical Institute, NY 10029, USA.
Chromosoma. 2011 Dec;120(6):621-32. doi: 10.1007/s00412-011-0337-6. Epub 2011 Aug 9.
Endogenous human centromeres form on megabase-sized arrays of tandemly repeated alpha satellite DNA. Human neocentromeres form epigenetically at ectopic sites devoid of alpha satellite DNA and permit analysis of centromeric DNA and chromatin organization. In this study, we present molecular cytogenetic and CENP-A chromatin immunoprecipitation (ChIP) on CHIP analyses of two neocentromeres that have formed in chromosome band 8q21 each with a unique DNA and CENP-A chromatin configuration. The first neocentromere was found on a neodicentric chromosome 8 with an inactivated endogenous centromere, where the centromeric activity and CENP-A domain were repositioned to band 8q21 on a large tandemly repeated DNA. This is the first example of a neocentromere forming on repetitive DNA, as all other mapped neocentromeres have formed on single copy DNA. Quantitative fluorescent in situ hybridization (FISH) analysis showed a 60% reduction in the alpha satellite array size at the inactive centromere compared to the active centromere on the normal chromosome 8. This neodicentric chromosome may provide insight into centromere inactivation and the role of tandem DNA in centromere structure. The second neocentromere was found on a neocentric ring chromosome that contained the 8q21 tandemly repeated DNA, although the neocentromere was localized to a different genomic region. Interestingly, this neocentromere is composed of two distinct CENP-A domains in bands 8q21 and 8q24, which are brought into closer proximity on the ring chromosome. This neocentromere suggests that chromosomal rearrangement and DNA breakage may be involved in neocentromere formation. These novel examples provide insight into the formation and structure of human neocentromeres.
内源性人类着丝粒在兆碱基大小的串联重复α卫星DNA阵列上形成。人类新着丝粒在缺乏α卫星DNA的异位位点上通过表观遗传方式形成，从而能够分析着丝粒DNA和染色质组织。在本研究中，我们对位于染色体带8q21上形成的两个新着丝粒进行了分子细胞遗传学和CENP-A染色质免疫沉淀（ChIP）分析，每个新着丝粒都具有独特的DNA和CENP-A染色质构型。第一个新着丝粒位于一条新双着丝粒染色体8上，其内源着丝粒失活，着丝粒活性和CENP-A结构域重新定位到一条大的串联重复DNA上的8q21带。这是新着丝粒在重复DNA上形成的首个例子，因为所有其他已定位的新着丝粒都在单拷贝DNA上形成。定量荧光原位杂交（FISH）分析显示，与正常染色体8上的活性着丝粒相比，失活着丝粒处的α卫星阵列大小减少了60%。这条新双着丝粒染色体可能为着丝粒失活以及串联DNA在着丝粒结构中的作用提供见解。第二个新着丝粒位于一条新着丝粒环形染色体上，该染色体包含8q21串联重复DNA，尽管新着丝粒定位于不同的基因组区域。有趣的是，这个新着丝粒由8q21和8q24带中的两个不同CENP-A结构域组成，它们在环形染色体上靠得更近。这个新着丝粒表明染色体重排和DNA断裂可能参与新着丝粒的形成。这些新例子为人类新着丝粒的形成和结构提供了见解。
