A multicopy insertion sequence in the bovine genome with structural homology to the long terminal repeats of retroviruses.

Abstract

Many of the transposable elements characterized so far in eukaryotes are a few thousand base pairs (bp) long and there are usually 20–50 copies per genome1. In addition, families of short interspersed repeated sequences have been discovered, some of which may also be transposable2. During analysis of the bovine satellite DNAs, I have found two types of sequence which have structural features in common with insertion elements3. They are only 0.6 and 1.2 kilobases (kb) long and are present in two different satellites at frequencies of 3.5 × 104 and 5 × 104 per genome, respectively. Sequence analysis of the 1.2-kb insertion and of satellite repeats carrying or lacking this sequence has now shown that a 6-bp duplication is generated at the site of insertion. I report here that the organization of this sequence is very similar to a retrovirus long terminal repeat (LTR). The 1.2-kb insertion and the related 0.6-kb sequence are highly homologous near their ends but unrelated in their internal sequences. These two elements may constitute precursors or descendants of an unknown retrovirus.