Kozlova Svetlana V, Mazurok Nina A, Vershinin Alexander V, Zakian Suren M
Institute of Cytology and Genetics, Russian Academy of Sciences, Siberian Department, Pr. ac. Lavrentieva, 10, Novosibirsk 630090, Russia.
Chromosome Res. 2003;11(8):759-69. doi: 10.1023/b:chro.0000005779.10547.06.
Different patterns of the DNA sequences organization were revealed in the vole (Rodentia) sex chromosome heterochromatin using dual-label fluorescence in-situ hybridization on extended DNA fibers with different repetitive DNA sequences as probes. In Microtus rossiaemeridionalis, the basic type represents the homogeneous relatively short tracks consisting of tandemly reiterated monomers of the MS3 family alternating with similar tracks of MS4 monomers and with non-fluorescent spacers. These tracks varied in the length of both repeats, with an average size of 12-22 kb or 3-5 copies. Apart from this, some continuous tracks of both families spanning 100-200 kb were interrupted by short spacers or single signals from the sequences with homology to LINEs. These results, together with that obtained by the analysis of phage clones of the genomic library, unequivocally demonstrate a variable large-scale DNA structural organization in heterochromatin of the M. rossiaemeridionalis sex chromosome. The dominant type of large-scale DNA organization in M. transcaspicus heterochromatin represents the unicolor relatively long tracks consisting of monotonous but not alternating monomers of MS3 or MS4 with sizes ranging from 15 to 40 kb and separated by extended spacers with an average length of 20 kb. Thus, the formation of the vole sex chromosome heterochromatic regions occurred relatively recently during speciation.
利用不同重复DNA序列作为探针，在伸展的DNA纤维上进行双标记荧光原位杂交，揭示了田鼠（啮齿目）性染色体异染色质中DNA序列组织的不同模式。在南俄草原田鼠中，基本类型是由MS3家族的串联重复单体与MS4单体的类似片段以及非荧光间隔区交替组成的相对较短的均匀片段。这些片段的两种重复序列长度各异，平均大小为12 - 22 kb或3 - 5个拷贝。除此之外，两个家族的一些连续片段跨越100 - 200 kb，被短间隔区或与LINEs具有同源性的序列的单个信号打断。这些结果，连同通过基因组文库噬菌体克隆分析获得的结果，明确证明了南俄草原田鼠性染色体异染色质中可变的大规模DNA结构组织。里海田鼠异染色质中大规模DNA组织的主要类型是由MS3或MS4的单调但不交替的单体组成的相对较长的单色片段，大小在15至40 kb之间，由平均长度为20 kb的延伸间隔区隔开。因此，田鼠性染色体异染色质区域的形成在物种形成过程中相对较晚发生。
