Fragments of LINE-1 retrotransposons flanked by inverted telomeric repeatsare present in the bovine genome. Homology with human LINE-1 elements

In the bovine genome we found two intrachromosomal DNA fragments flanked by inverted telomeric repeats (GenBank Accession Nos. AF136741 and AF136742). The internal parts of the fragments are homologous exclusively to the huma n sequences and to the consensus sequence of the L1MC4 subfamily of LINE-1 retrotransposons which are widespread among mammalian genomes. We found tha t distribution of homologous human sequences within our fragments is not ra ndom, reflecting a complicated pattern of insertion mechanisms of and maint enance of retrotransposons in mammalian genomes. One of the possible explanations of the origin of LINE-1 truncated elements flanked by inverted telomeric repeats in the bovine genome is that extrach romosomal DNA fragments may be modified by telomerase and subsequently, tra nsferred into chromosomal DNA.