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J. A. Marchal M. J. Acosta M. Bullejos E. Puerma R. Díaz de la Guardia A. Sánchez 《Chromosome research》2006,14(2):177-186
Long interspersed nuclear elements (L1 or LINE-1) are the most abundant and active retroposons in the mammalian genome. Traditionally,
the bulk of L1 sequences have been explained by the ‘selfish DNA’ hypothesis; however, recently it has been also argued that
L1s could play an important role in genome and gene organizations. The non-random chromosomal distribution of these retroelements
is a striking feature considered to reflect this functionality. In the present study we have cloned and analyzed three different
L1 fragments from the genome of the rodent Microtus cabrerae. In addition, we have examined the chromosomal distribution of this L1 in several species of Microtus, a very interesting group owing to the presence in some species of enlarged (‘giant’) sex chromosomes. Interestingly, in
all species analyzed, L1-retroposons have preferentially accumulated on both the giant- and the normal-sized sex chromosomes
compared with the autosomes. Also we have demonstrated that L1-retroposons are not similarly distributed among the heterochromatic
blocks of the giant sex chromosomes in M. cabrerae and M. agrestis, which suggest that L1 retroposition and amplification over the sex heterochromatin have been different and independent processes
in each species. Finally, we proposed that the main factors responsible for the L1 distribution on the mammalian sex chromosomes
are the heterochromatic nature of the Y chromosome and the possible role of L1 sequences during the X-inactivation process. 相似文献