Sequential de novo centromere formation and inactivation on a chromosomal fragment in maize
Sequential de novo centromere formation and inactivation on a chromosomal fragment in maize
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玉米染色体片段的顺序从头着丝粒形成和失活
DOI：
10.1073/pnas.1418248112
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发表时间：
2015-03-17
影响因子：
11.1
通讯作者：
Han, Fangpu
中科院分区：
文献类型：
--
作者：
Liu, Yalin;Su, Handong;Han, Fangpu
着丝粒是染色体上参与有丝分裂和减数分裂运动的部分。着丝粒的活性是表观遗传的，因为潜在的DNA序列不一定决定功能。在本研究中，跟踪了一个染色体片段，其中活性着丝粒的位置发生了连续的从头形成和失活。结果表明，从头着丝粒的形成发生规律。然而，当与以前的研究结果相结合，即较大的着丝粒可以覆盖较小的着丝粒，当一起存在时，它被假设，这种频繁的从头着丝粒的形成是从正常的染色体上清除失活，但可以持续在结构上无着丝粒的片段和遗传。着丝粒在活性和非活性状态之间交替的能力表明控制着丝粒组装和功能的重要表观遗传方面。在玉米（Zea mays）中，B染色体着丝粒在与9号染色体（TB-9 Sb）的短臂易位上的错误分裂可产生具有不同着丝粒大小和着丝粒DNA序列的许多变体。在TB-9 Sb的这些衍生物中，我们在染色体衍生物3-3上发现了一个从头着丝粒，其没有典型的着丝粒重复序列。该着丝粒来源于9号染色体短臂上的288-kb区域，并且距离TB-9 Sb中9号染色体的易位断裂点19 Mb。从衍生物3-3中删除了祖细胞telo 2 -2中的功能性B着丝粒，但保留了一些B重复序列。衍生物3-3的从头着丝粒在另外三个衍生物中变得无活性，在每个染色体上的其他地方形成新的着丝粒。我们的研究结果表明，从头着丝粒启动是很常见的，可以持续染色体片段没有一个典型的着丝粒。然而，我们假设，当从头着丝粒开始反对一个更大的正常着丝粒，他们从染色体上清除失活，从而保持核型的完整性。
Significance The centromere is the part of the chromosome that is involved with movement in mitosis and meiosis. The activity of the centromere is epigenetic in that the underlying DNA sequences do not necessarily determine function. In the present study, a chromosomal fragment was followed in which a sequential de novo formation and inactivation occurred for the position of the active centromere. The results suggest that de novo centromere formation occurs regularly. However, when coupled with previous findings that larger centromeres can inactivate smaller ones when present together, it is hypothesized that such frequent de novo centromere formations are cleared from normal chromosomes by inactivation, but can persist on structurally acentric fragments and be inherited. The ability of centromeres to alternate between active and inactive states indicates significant epigenetic aspects controlling centromere assembly and function. In maize (Zea mays), misdivision of the B chromosome centromere on a translocation with the short arm of chromosome 9 (TB-9Sb) can produce many variants with varying centromere sizes and centromeric DNA sequences. In such derivatives of TB-9Sb, we found a de novo centromere on chromosome derivative 3-3, which has no canonical centromeric repeat sequences. This centromere is derived from a 288-kb region on the short arm of chromosome 9, and is 19 megabases (Mb) removed from the translocation breakpoint of chromosome 9 in TB-9Sb. The functional B centromere in progenitor telo2-2 is deleted from derivative 3-3, but some B-repeat sequences remain. The de novo centromere of derivative 3-3 becomes inactive in three further derivatives with new centromeres being formed elsewhere on each chromosome. Our results suggest that de novo centromere initiation is quite common and can persist on chromosomal fragments without a canonical centromere. However, we hypothesize that when de novo centromeres are initiated in opposition to a larger normal centromere, they are cleared from the chromosome by inactivation, thus maintaining karyotype integrity.