Molecular Cytogenetic Characterization of C-Band-Positive Heterochromatin of the Greater Long-Tailed Hamster (<b><i>Tscherskia triton</i></b>, Cricetinae)

Abstract

The greater long-tailed hamster (<i>Tscherskia triton</i>, 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 <i>Taq</i>I-digested genomic DNA and then characterized them by chromosome in situ and filter hybridization. The <i>Taq</i>I-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 (<i>Mesocricetus</i>, <i>Cricetulus</i>, and <i>Phodopus</i>). These results suggest that the 110-bp and 405-bp repeats rapidly diverged in the lineage of <i>T. triton</i>, 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 <i>T. triton</i>.