Kamimura Eikichi, Uno Yoshinobu, Yamada Kazuhiko, Nishida Chizuko, Matsuda Yoichi
Institute for Experimental Animals, Research Center for Experimental Modeling of Human Disease, Kanazawa University, Kanazawa, Japan.
Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan.
Cytogenet Genome Res. 2022;162(6):323-333. doi: 10.1159/000527478. Epub 2022 Dec 19.
The greater long-tailed hamster (Tscherskia triton, Cricetinae) has a unique karyotype (2n = 28), containing 11 pairs of acrocentric chromosomes with large C-band-positive centromeric heterochromatin blocks. To understand the origin and evolutionary process of heterochromatin in this species, we isolated novel families of chromosome site-specific highly repetitive DNA sequences from TaqI-digested genomic DNA and then characterized them by chromosome in situ and filter hybridization. The TaqI-families of repetitive sequences were classified into 2 types by their genome organization and chromosomal distribution: the 110-bp repeated sequence organized in large tandem arrays (as satellite DNA), localized to centromeric C-positive heterochromatin of acrocentric autosomes (chromosomes 1-11) and submetacentric X chromosome, and the 405-bp repeated sequence that was composed of 30-32-bp internal repeats, distributed in the pericentromeric region on the short arms of X and Y chromosomes. The repetitive sequences did not cross-hybridize with genomic DNA of any genera of Cricetinae (Mesocricetus, Cricetulus, and Phodopus). These results suggest that the 110-bp and 405-bp repeats rapidly diverged in the lineage of T. triton, evolving in a concerted manner among autosomes and X chromosome and within X and Y chromosomes, respectively. The 110-bp centromeric repeat contained a 17-bp motif in which 9 bases are essential for binding with the centromere-associated protein CENP-B, suggesting the possibility that the 110-bp major satellite DNA carrying the 17-bp motif may have a role in the formation of specified structure and/or function of centromeres in T. triton.
大仓鼠（Tscherskia triton，仓鼠亚科）具有独特的核型（2n = 28），包含11对近端着丝粒染色体，其着丝粒异染色质块具有大的C带阳性。为了解该物种异染色质的起源和进化过程，我们从TaqI酶切的基因组DNA中分离出染色体位点特异性高度重复DNA序列的新家族，然后通过染色体原位杂交和滤膜杂交对其进行表征。根据其基因组组织和染色体分布，TaqI重复序列家族分为2种类型：110 bp重复序列以大串联阵列形式组织（作为卫星DNA），定位于近端着丝粒常染色体（染色体1 - 11）和亚中着丝粒X染色体的着丝粒C阳性异染色质上；405 bp重复序列由30 - 32 bp的内部重复序列组成，分布在X和Y染色体短臂的着丝粒周围区域。这些重复序列与仓鼠亚科（金仓鼠属、仓鼠属和毛足鼠属）任何属的基因组DNA均无交叉杂交。这些结果表明，110 bp和405 bp重复序列在大仓鼠谱系中迅速分化，分别在常染色体和X染色体之间以及X和Y染色体内部以协同方式进化。110 bp着丝粒重复序列包含一个17 bp的基序，其中9个碱基对于与着丝粒相关蛋白CENP - B结合至关重要，这表明携带17 bp基序的110 bp主要卫星DNA可能在大仓鼠着丝粒特定结构和/或功能的形成中发挥作用。
